Advances in Pasture Management and Animal Nutrition to Optimize Beef Cattle Production in Grazing Systems

*Andressa Scholz Berça, Eliéder Prates Romanzini, Abmael da Silva Cardoso, Luís Eduardo Ferreira, André Pastori D'Aurea, Lauriston Bertelli Fernandes and Ricardo Andrade Reis*

#### **Abstract**

The increasing demand of meat requires the adoption of sustainable intensification livestock systems, applying nutritional strategies to reduce any negative contribution from beef cattle to global warming and, at the same time, to increase animal performance and productive efficiency. The pasture management practices and feed supplementation, mainly using non-edible feed with less costs, could minimize environmental and social impacts, resulting in higher productivity with less inputs utilization. Tropical grass submitted to grazing management according to plant height present high soluble protein and low levels of indigestible neutral detergent fiber contents. Energy or rumen undegradable protein supplementation, associated to alternative additives to antibiotics effects, such as probiotics, tannin, essential oils and saponin, can help to fully exploit the animal genetic potential and nutrient utilization efficiency, which decreases greenhouse gases emissions and improves animal performance. Hence, more information about these tools can make the livestock systems in tropical pasture more efficient and eco-friendlier.

**Keywords:** greenhouse gases, non-edible feed, organic feed additive, supplementation, tropical pastures

#### **1. Introduction**

The large territorial extension and the tropical climate favorable to the growth of tropical grasses make pastures the basis for feeding Brazilian beef cattle, being the most practical and economical source to feed cattle in Brazil [1], responsible for the production of 89% of the entire herd, which reaches almost 188 million heads [2].

The economy globalization induces agriculture to become more and more efficient and competitive, therefore, failures in pasture management can be decisive in the

success or unsuccess of beef cattle livestock [3]. In this sense, the great challenge of beef cattle production systems on pastures is the use of practices capable to increase the productivity and quality of meat with low environmental impact [4, 5]. For this, enhancing the animal performance and optimizing the use of basal forage resources is the main objective of management strategies to be adopted [6].

In Central Brazil, tropical forages present as a typical characteristic the seasonality of production, concentrating its growth between 70 and 80% in the rainy season, and 20 to 30% in the dry season [7]. The effects of this seasonality in beef cattle are evident through drastic variations in the chemical and structural composition of the forage canopy, which directly reflect on intake, digestibility, and weight gain and, consequently, delay the slaughter age of the animals [8]. The rainy season presents advantages for ruminant production as it has favorable edaphoclimatic conditions for the green leaf and forage mass productions with higher levels of crude protein (CP) and total digestible nutrients (TDN), when compared to the dry season, in addition to be the time to explore the maximum of animal performance and gain per area [9].

In theory, high-quality tropical forages should be able to provide the nutrients needed to meet grazing animals' requirement, including energy, protein, minerals and vitamins. However, the chemical composition of tropical grass forage is rarely in a state of balance between animal requirements and the nutrients needed to obtain high weight gains, due to the quantitative and qualitative seasonality inherent to the pasture system, interfering in the expression of the genetic potential of beef cattle in Brazil [10]. In this sense, the management strategies adopted by the manager can provide differences in the magnitude of responses in animal performance and weight gain per explored pasture area [11].

The intensification of the production system requires, in addition to the use of pasture management techniques, the adoption of nutritional strategies, such as the diet supplementation of grazing cattle, as well as the use of the genetic potential of the animals, through selection and crossings. Such strategies must be consolidated in order to ensure the profitability of the production system, sustainability of the pasture ecosystem and production of quality meat for the consumer market [5, 6]. Faced with such conditions, the search for alternatives to chemical additives that reduce the negative contribution of livestock to global warming and, at the same time, increase performance and productive efficiency is increasing [12]. In this context, the use of organic additives has been established, among these components are condensed tannins, saponins and essential oils. These compounds come from plants, usually its extracts, and have the ability to manipulate ruminal fermentation and animal metabolism, in order to increase performance and promote beneficial effects to the environment [13].

Therefore, this chapter aimed to address aspects related to the production of beef cattle from a sustainable perspective, considering grazing management, the strategic use of diet supplementation for grazing animals, featuring the inclusion of non-edible feed and organic additives on supplement composition and their results.

#### **2. Aspects related to beef cattle in grazing systems**

#### **2.1 Livestock contribution to greenhouse gases**

As the largest land use system in Brazil, the agricultural sector contributes 40% of the global agricultural gross domestic product, provides income for more than 1.3 billion people and food for at least 800 million people, using vast areas of pasture and *Advances in Pasture Management and Animal Nutrition to Optimize Beef Cattle Production… DOI: http://dx.doi.org/10.5772/intechopen.99687*

a third of agricultural land for food production in the world [14]. However, although it assumes great importance in the economic scenario and is essential for world food, the rapid population growth and the production and consumption of agricultural products is contributing to a substantial emission of greenhouse gases (GHG) to the environment, being responsible for 14.5% of the total human induced GHG emissions in the world [15], which makes the activity often cited as the villain of global warming [16].

Livestock contributes to GHG emissions in the form of methane (CH4) from enteric fermentation, nitrous oxide (N2O) from the use of nitrogen (N) fertilizers, and CH4 and N2O from animal excreta management and deposition. Furthermore, carbon dioxide (CO2) is also produced from the use of fossil fuel and energy on farms [5].

The production of enteric CH4 by ruminants is a fundamental process for the adequate functioning of the digestive system of these animals, but it results in a loss of gross ingested energy and, consequently, reduces animal performance [16], in addition to having its contribution in 3.5% of the world's total GHG emissions [17]. Worldwide, CH4 is considered the second largest contributor to global warming (16%), right after CO2 (65%) [17]. The gas from livestock systems originates mainly from enteric fermentation (90%), being the rest produced from the fermentation of animal organic waste [18].

The use of N fertilizers and the deposition of animal excreta (feces and urine) are the main responsible for the losses of N to the environment, causing not only economic losses, but also environmental ones, due to nitrate leaching, volatilization of ammonia (NH3) and, mainly, N2O emission [19]. It is estimated that the annual global losses of N via excreta represent almost 26 million tons, and N fertilizers, 17 million tons [20]. The Intergovernmental Panel on Climate Change [17] estimates NH3 volatilization values of 30% (20–50%) of excreta (urine and feces) and 15% (3–43%) of the urea fertilizer.

Although ruminants contribute with gas emissions to the environment, management strategies are essential for the sustainability of the global food system. In general, the practices involve improving the environmental performance of livestock systems through the management, supplementation, and adequate use of alternative additives to antibiotics; establish sustainable levels of intake of foods of animal origin, as well as using ingredients that are not consumed by humans (non-edible feed) [21, 22].

Indications for reducing CH4 production include measures that reflect better animal performance and result in shorter production cycles, involving improvement in the composition and quality of forage, by reducing the cell wall and increasing levels of soluble protein and carbohydrates, e.g., improvement of animal genetics, feed supplementation [23]. Furthermore, the use of substances such as additives composed of organic acids, yeast and plant extracts, such as tannin and saponin, also help to reduce methanogenesis by manipulating ruminal fermentation [22].

A common strategy to reduce N losses in the system, both directly through N excretion via feces and urine, and indirectly through the use of fertilizers, is the mixed pastures of grass and legume, due to its association with nitrogen-fixing bacteria, which increases forage productivity and nutritive value [19]. The improvement in the diet quality, in turn, can change the urine and feces composition and, consequently, N losses through excreta [24].

#### **2.2 Grazing management**

Animal performance in pastures is mainly determined by forage quality, which is a function of dry matter (DM) intake and forage nutritive value [8]. In turn, the nutritive value is determined by the chemical composition and the nutrients directly responsible for the DM digestibility, CP and neutral detergent fiber (NDF) contents [8]. In this sense, the correct management of pastures affects both pasture chemical composition and structure, in addition to factors such as forage mass, supply of leaves, stem and dead material, which are determinants in the animal ingestive behavior and, consequently, in the nutrient's intake [25].

During the rainy season, the management must be done through strategies that guarantee the longest duration in the supply of quality forage and/or the improvement of forage nutritive value, aiming to achieve greater productivity of the system [26]. In this sense, pasture management should prioritize the adjustment in grazing intensity to obtain high yields per animal and per area, considering the morphophysiological principles that govern the plant growth and its biological limits, in order to allow persistence of the pasture and avoid its degradation [12]. Any management criteria to be adopted, therefore, must consider the adjustment of forage allowance and stocking rate in order to simultaneously control the quality and quantity of available forage and maintain the sustainability of the system [11].

In general, pasture management involves a set of practices aimed at changing the morphology or delaying plant maturity, in order to increase the level of digestible nutrients in the diet for cattle and ensure adequate performance [27]. Furthermore, Sollenberger et al. [28] reported that grazing management should allow for a balance between plant growth, intake, and animal production, to keep a stable production system.

According to Pereira et al. [29], the control of pasture defoliation is crucial to the sustainability of the system, as it is an antagonistic event, that is, the plant uses the leaves to capture light and carry out photosynthesis, producing carbohydrates that allow the maintenance of life and of development. On the other hand, the leaf is the morphological component with the highest nutritive value that compose most of the diet of grazing animals [25]. Therefore, it is necessary to adopt management techniques that prioritize the forage plant and the grazing animal, allowing high forage productivity combined with high animal performance [5].

#### *2.2.1 Grazing height*

Pasture management based on the adjustment of grazing intensity can be done following several criteria, such as grazing pressure, forage allowance, residual forage mass, residual leaf area index (LAI), height, and others [11]. The adoption of height as a management criterion allows the control of forage mass and stocking rate, being able to relate pasture growth with its use and, consequently, with the canopy structure and responses in intake and animal performance [30]. In addition, height is a functional and practical field indicator, which can be correlated to other management criteria, such as forage allowance and light interception (LI) [31]. Also, grazing height directly affects the ingestive behavior of grazing animals [5].

According to Reis et al. [8], grazing management must adjust the frequency and intensity of defoliation, so that the animal can harvest forage at the appropriate physiological age, which directly affects the nature and concentration of structural carbohydrates in the cell wall and nitrogenous compounds, which are the main determinants of forage quality. Thus, the authors report that pastures kept under continuous stocking and efficiently managed can provide continuous intake of young leaves and, consequently, greater forage digestibility when compared to the intermittent stocking system.

#### *Advances in Pasture Management and Animal Nutrition to Optimize Beef Cattle Production… DOI: http://dx.doi.org/10.5772/intechopen.99687*

Pasture management under different grazing intensities promotes different responses in forage mass accumulation and nutritive value. Studies conducted at FCAV/Unesp Campus de Jaboticabal, Brazil generated consistent data on the effects of different heights of tropical pasture management in the rainy season [30, 32–37]. The afore mentioned authors evaluated Marandu grass pastures in a continuous stocking and variable stock grazing system, at three heights: 15, 25 and 35 cm. As the grazing height increased, there was a reduction in CP and an increase in fiber contents, higher senescence rate and higher leaf elongation rate, the latter two being related to higher LAI, which intercepts a greater amount of solar radiation. On the other hand, canopies kept at a lower height showed reduced growth and senescence, lower forage accumulation, and restriction in the green material allowance, which limited intake and animal performance. In summary, the authors concluded that Marandu grass pastures managed under continuous stocking, during the rainy season, should be managed at 25 cm height, in order to maximize forage intake and individual daily weight gain in the growing phase, without a marked decline in weight gain per area.

In this sequence of studies, Marandu grass pastures managed under continuous stocking at 25 cm height corresponded to 95% of LI and, according to Delevatti et al. [38], this management results in pastures with a higher proportion of leaves, higher protein fraction, lower proportions of dead material and insoluble neutral detergent fiber (iNDF).

In Marandu grass pastures subjected to rotational grazing, 95% LI values during regrowth were also obtained with an average sward pre-grazing height of around 25 cm [39, 40]. According to Pedreira et al. [40], the management strategy of entering animals at 95% LI reduces the amount of self-shadowed material in the canopy and, therefore, reduces tissue death. Furthermore, in a rotational system, the height of the post-grazing residue interferes in the pasture intake due to changes in the canopy structure and the stratum explored by the animals during grazing [39].

#### *2.2.2 Nitrogen fertilization*

According to Reis et al. [11], the growth, development and chemical composition of forages are determining factors in animal performance, and, in turn, are affected by physiological aspects inherent to the plant and environmental conditions. Thus, N is the most limiting element for the development of forage grasses, due to the amount of nutrient extracted by the plant and the low residual effect of N in the soil after its application, also to losses through volatilization, leaching and immobilization by microorganisms [41].

In this scenario, the use of fertilization in pastures has been intensified in recent years, aiming to increasing the forage nutritive value and the stocking rate, which, consequently, increases the production per unit of area [38]. The pasture stocking rate, in turn, depends directly on the productivity of the forage plant, which is affected by several factors such as precipitation, temperature, light intensity, soil fertility and fertilization, especially with N [42].

According to Rezende et al. [43], the effect of N fertilization on yield is related to the initial tillering after cutting, as it promotes rapid expansion of the leaves, quickly replenishing photosynthetic tissues and increases tillers formation, responsible for higher DM production. In addition, N fertilization increases the concentration of CP, decreases N insoluble in neutral detergent and allows for greater efficiency in the rumen microbiota cellulolytic activity, factors that optimize animal performance [6]. The efficiency of N utilization by forage plants, however, is quite divergent, ranging from 5 to 89.2 kg of DM/kg of N applied [44].

The CP ruminal degradability of tropical and temperate forage plants is naturally high and increases with increasing N dose applied to the pasture [6]. Specially in tropical grass pasture management situations in which the high degradability of N compounds associated to the high content of structural carbohydrates with slow degradation is observed, the lack of balance between N and carbon skeletons arising from the degradation of carbohydrates in the rumen, compromises efficiency of nitrogen use (ENU) and microbial protein synthesis [45]. This condition, however, generates excessive losses of N compounds in the ruminal environment in NH3 form in the urine, generating a protein deficit in relation to the requirements for high gains [9], which, in addition to resulting in economic losses, can be harmful to the environment through N losses in the form of volatilized NH3, N2O emission and nitrate leaching [4, 46].

In summary, pasture management practices during the rainy season, including maintenance N fertilization, adjustment in stocking according to the amount of forage available, provide pasture persistence, which surely dilutes production costs and gas emissions resulting from the inadequate land use and the prolonged period of pasture use [8].

#### **2.3 Diet supplementation**

In intensive production systems, supplementation is adopted as a technological tool to enhance the pastures use, aiming a compatible production with the genetic merit of the animals and profitability [27]. In general, supplementation allows the production of earlier animals, the increase in pastures support capacity, higher gain per animal and per area, the reduction of the time needed to reach slaughter weight, which, consequently, shortens the rearing and finishing grazing animals, in addition to the production of better-quality meat and carcass [9].

Thus, there is an increase in livestock offtake rates and a rapid turnover of invested capital, improving the efficiency and profitability of this system [47]. Furthermore, in grazing management systems that aims to optimize performance per animal and per area, it is possible to minimize the environmental impacts of beef cattle production in tropical grass pastures [4, 48].

The amount of protein and energy needed to optimize the use of nutrients, however, will depend on the pasture chemical composition and the crude protein/ digestible organic matter (DOM) ratio, since ENU depends on the energy availability [11]. Therefore, supplementation must be preceded by the characterization of the quantity and quality of available forage, especially regarding the characteristics of carbohydrates and N compounds, to ensure the supply of nutrients that limit ruminal microbial activity [33].

#### *2.3.1 Supplementation during dry season*

Under conditions in Central Brazil, dry season is the most critical phase of grazing cattle production system. During this season, animals consume forage with low nutritional value, characterized by a high content of indigestible fiber and CP contents below critical level (7% CP), thus limiting its intake and, consequently, productive performance [27, 49]. Therefore, if there is no supplementation of cattle diet during this season, in order to supply the deficient nutrients of forage, there will be a reduction in weight gain or even negative performance, since the body nutrients are

#### *Advances in Pasture Management and Animal Nutrition to Optimize Beef Cattle Production… DOI: http://dx.doi.org/10.5772/intechopen.99687*

mobilized for maintenance, increasing the slaughter age, the fixed cost of the activity, and reducing livestock offtake rates [8].

According to Reis et al. [11], in the dry season, protein is the most limiting nutrient and, therefore, the one with the greatest need for supplementation, since it is a determinant in the capacity for fibrous substrates degradation by ruminal microorganisms and, consequently, in the passage rate and dry matter intake. In this sense, strategic supplementation during dry season involves the supply of protein, considering the ruminal events of digestion, fermentation, synthesis of N compounds and intake of low-quality forage. The live weight gains obtained through supplementation at this phase can be low, ensuring maintenance of animal weight, moderate (up to 300 g/ animal/d), and even high (from 600 to 700 g/animal/d), enabling earlier slaughter of animals [8]. An advantageous alternative is the use of multiple supplements (protein and energy), which result in gains in the order of 150 to 300 g/animal/d with 0.5 to 2% BW and 700 to 1000 g/animal/d with 8 to 10% BW supplement.

#### *2.3.2 Supplementation during rainy season*

Although the rainy season is characterized by presenting edaphoclimatic conditions favorable to forage production, the way in which these conditions occur, associated to the management strategies adopted and the interactions between pasture quality and quantity and nutrient supply via supplement, can provide differences in the magnitude of responses to supplementation on animal performance and gain per area [48].

During this period, when forages are classified as medium to high-quality, with N compounds above the minimum recommended (7% CP) for full activity of bacteria using structural carbohydrates and with levels of rumen ammonia (N-NH3) above 5 mg/dL, the objective of supplementation associated with grazing management strategies that maximize the production of grazing stratum, is to prevent deleterious effects in the use of potentially digestible NDF (pdNDF) in forage [49, 50]. According to Huhtanen et al. [50], pdNDF is a nutritionally more adequate entity for evaluating forage quality and corresponds to the portion of NDF that is potentially digested by ruminal microorganisms, and the digested amount is related to the retention time in the fermentation compartments, being short to complete the digestion of all the ingested pdNDF.

According to Santos et al. [51], values of average daily gain (ADG) above 800 g during the rainy season are hardly reached by cattle kept in tropical pastures without the use of supplementation with concentrate. Despite the high cost of the additional gains inherent to the concentrate in this period (100 to 200 g/animal/day), this can result in a considerable reduction in finishing phase time, on pasture or feedlot, with possible economic returns [6, 33, 36, 52].

#### *2.3.3 Energy supplementation*

The main objective of grazing cattle supplementation is to increase the intake of energy and nutrients relative to those found in exclusive pasture diets [27]. When forage and easily fermentable carbohydrates are provided, fibrolytic microorganisms must compete with non-fibrous carbohydrate (NFC) for substrates such as NH3, peptides, sulfur, and branched-chain carbon skeletons for their growth. An adequate supplementation strategy would be to maximize the use of forage by optimizing

its digestion, increasing the passage rate of indigestible residue, and consequently increasing the intake of TDN [9].

According to Poppi and McLennan [26], high weight gains depend mainly on the supply of amino acids and energy transported to bovine tissues, a condition that is rare in animals under exclusive grazing. In this context, the same authors reported that energy supply can be an effective strategy to provide extra protein to the animal, as it allows NH3, which is usually lost in urine, feces, or saliva, to be captured and incorporated into microbial protein. Microbial protein production, in turn, varies depending on the nature of the energy substrate supplied, such as starch, soluble fiber, pectin or sugars [53].

In intensive production systems, tropical grasses managed with high N doses (200 to 500 kg/N/ha) during the rainy season present about 40 to 50% of nitrogenous compound content in soluble form [54]. This fact, associated with the high content of structural carbohydrates with lower degradation rates, promotes a lack of synchrony between N and carbon skeletons arising from the degradation of carbohydrates in the rumen, disfavoring microbial protein synthesis and the efficiency of ruminal N-NH3 utilization [26].

For Poppi and McLennan [26], this condition causes excessive losses of nitrogenous compounds in the ruminal environment in the NH3 form, decreasing the microbial protein synthesis and generating a metabolizable protein (MP) deficit in relation to the requirements for high gains. Also, according to the researchers, maximum efficiency in microbial protein synthesis is reached when 160 g CP/kg DOM is observed, while values close to 210 g CP/kg DOM result in appreciable N loss.

According to Reis et al. [8], the main limitations for ruminal microbial growth would be related to the forage available for grazing, allowing low assimilation of available N in ruminal microbial protein, due to the high degradability of N compounds or lower carbohydrate degradation rate from fibrous forage. Thus, the supply of energy supplements with sources of rapid availability in the rumen can promote better animal performance by optimizing the microbial assimilation of N from N compounds with high degradability in the forage [45].

In a review by Reis et al. [11], the authors reported that during the rainy season, tropical grasses have DM digestibility between 55 and 65%, in addition to CP between 7.9 and 17.4% in their composition, which can result in different CP/DOM ratios. Assessing experiments conducted in the rainy season, it was observed that even in animals receiving only mineral salt, ruminal N-NH3 values are above the critical level of 5 mg/dL of rumen fluid [30, 34]. However, only when the animals were supplemented, in the first 6 hours after supplementation, optimal levels of N-NH3 were found in the rumen for maximum microbial growth, i.e., greater than 20 mg of N-NH3/dL of ruminal fluid.

According to Leng [55], the inclusion of grains in roughage diets can reduce fiber digestibility, and this phenomenon is inherent to two effects that interfere in cellulolytic bacteria growth: a specific effect (drop in pH) and a non-specific (carbohydrate effect). In ruminants raised on tropical pastures, the variation in ruminal pH as a function of dietary supplementation seems to be relatively small, not affecting growth of bacteria that use fibrous carbohydrates. In this sense, the availability of soluble carbohydrates is responsible for the depression of fiber digestibility, as reported by Rooke et al. [56] and Huhtanen [57], reflecting the high effectiveness of long fibers that act in the maintenance of ruminal conditions [58].

The goal of a supplementation program for grazing animals is, therefore, to satisfy their requirements through an interactive and associative action between the basal

forage and the supplemental sources. Thus, it is possible to enhance the positive associative effects and minimize negative interactions, in order to increase intake and optimize forage use, and not only the direct meeting of animal requirements via supplement [27].

#### *2.3.4 Protein supplementation*

Protein is the main limitation in cattle production systems on tropical pasture both in the dry and rainy seasons, especially when the pastures have low nutritive value [59]. At that time, although some tropical grasses have CP levels that meet the animal's nutritional requirements, part of this protein may be unavailable to the action of ruminal microorganisms, as it is linked to fibrous fraction [8]. Therefore, the formulation of a protein or protein-energy supplement for grazing cattle must consider the protein fraction available of forage, to provide enough N to use the energy substrates contained in the plant, such as digestible cellulose and hemicellulose [33].

The additional supply of N for animals consuming low nutritive value forage favors the growth of fibrolytic bacteria, increases the digestibility and microbial protein synthesis and, thus, allows to increase the voluntary intake of forage and improve the energy balance of the grazing animal [60]. The success of this supplementation strategy is associated to characteristics of pdNDF fraction, which will be the main source of energy to meet the demand of microorganisms [11]. Once the N requirements for the maintenance of ruminal microorganisms are met, the supplement can provide protein and energy for additional gains, according to the desired performance [60].

According to Pathak [61], cattle need two types of protein: rumen degradable protein (RDP), which is necessary to meet the requirements of ruminal microorganisms, and rumen undegraded protein (RUP), to meet the requirements of animals. In this scenario, dietary protein acts as a source of MP for ruminants, which in turn corresponds to the sum of the microbial protein synthesized from the RDP, with the RUP absorbed in the intestine.

Microbial protein synthesis depends on adequate sources of N and carbohydrates. In this sense, Rodríguez et al. [62] report that the structure of dietary proteins defines their degradation in the rumen and the contribution to available N to microorganisms. Ammonia is the main source of N in rumen microorganisms, but the availability of amino acids, peptides, and both increase the growth of cellulolytic and amylolytic bacteria [63], mainly due to direct incorporation into microbial protein or increased availability of carbon skeletons that can be used as an energy source or in the synthesis of microbial amino acids [64].

In mixed forage and concentrate diets, microbial protein synthesis can be increased due to better synchronization of nutrient release, adequate ruminal environment for maintenance of different species of microorganisms, increased amounts and types of substrates, higher nutrient intake and, consequently, an increase in the rate of passage of solids and liquids [65]. While forages can supply N as highly degradable protein or non-protein nitrogen (NPN), concentrates can supply N primarily as peptides and/or amino acids needed for microbial protein synthesis [26]. According to Pathak [61], efficiency tends to increase when readily fermentable carbohydrate is supplemented in less than 30% of the total diet but decreases when the level of supplementation is greater than 70%.

In pasture systems, even during rainy season, the synchronism between protein and energy in the rumen is rarely achieved, due to variations in forage quality and different

rates of substrate utilization [7]. However, urea recycling is an important ruminant mechanism, capable of ensuring adequate levels of N-NH3 in the rumen throughout the day, however when there is excess protein in the diet, there may be losses of N to the environment [9]. In this sense, the great challenge in choosing the sources and amount of CP in the supplement is to equate its use according to energy availability, ensuring adequate levels of N-NH3 and minimizing losses in feces and urine [9].

Protein supplements can be composed by two protein sources: true protein and NPN. True protein sources have different RDP contents, such as cottonseed meal and corn gluten, which have about 65 and 18% RDP in their composition, respectively [66].

Non-protein nitrogen sources are completely soluble in the rumen and used by ruminal bacteria for microbial protein synthesis, and its use is common, mainly due to its lower cost, when compared to other conventional protein source, such as soybean meal [67]. According to Araújo et al. [68], the main source of NPN used in Brazil is urea, which has become an advantageous alternative by its easy availability in the market, high concentration of N in its composition and low unit cost. Additionally, urea is a source of N-NH3 for fibrolytic microorganisms and, because of its low acceptability, it can be used as a controlling agent for supplement intake by animals. However, it is essential to respect the limits of urea inclusion in the diet, to avoid causing poisoning in animals and high N loss in urine. For more efficient use of nutrients, urea should be mixed with energy components rich in non-fibrous carbohydrates, true protein, and sulfur.

In pasture production systems, it is necessary to optimize the use of nutrients and forage digestibility to maximize weight gain, even though the supplement promotes direct input of nutrients required by animal [66]. In this scenario, protein supplementation can increase forage intake due to the supply of N-NH3 to ruminal microorganisms, and a consequent increase in energy intake, responsible for the increase in animal performance. However, the intensity of the response to a protein supplement will depend on pasture availability and quality [33].

#### **2.4 Non-edible feed**

In animal nutrition, corn is the main ingredient in energy supplements, and contains around 72% starch, 9% CP, low fiber content, in addition to being the largest source of metabolizable energy (ME) among cereals [69]. However, corn is an ingredient traditionally consumed by humans and monogastric animals which, in the context of system sustainability, generates competition between livestock and society [70]. Likewise, cottonseed meal and soybean meal are the most conventionally used protein ingredients in animal feed, due to the high CP content, which varies between 30 and 50%, and RUP, which contributes to increase the protein flow to the intestine [71–73]. Despite being important protein sources, they are costly ingredients that increase the production costs of beef cattle systems.

In the search for alternative feed not consumed by humans and for less costly ingredients in cattle nutrition, agroindustry co-products have gained prominence in the market and in research, especially in Brazil.

#### *2.4.1 Citrus pulp*

The orange juice and other citrus fruit industry, whose production leadership is in Brazil, generates bagasse or citrus pulp as a co-product, which comprises between *Advances in Pasture Management and Animal Nutrition to Optimize Beef Cattle Production… DOI: http://dx.doi.org/10.5772/intechopen.99687*

45 and 58% of the total fruit, consisting of peels, membranes, vesicles, and seeds of orange or another citrus. Nutritionally, it is characterized as an intermediate product between roughage and concentrates, rich in pectin, cellulose, and hemicellulose polysaccharides [74, 75].

Citrus pulp has been widely used to replace corn, presenting in its composition 85–90% of the energy value of this ingredient [76], in addition to having little or no negative effect on ruminal fermentation compared to starch-rich diets [74] .

In general, the pulp is characterized by high DM digestibility, high soluble fiber content, high soluble carbohydrate content and highly digestible cell wall [77]. In its chemical composition, citrus pulp has approximately 89–90% DM; 6–11% CP; 2–12% of ether extract (EE), this value depending on whether or not the oils are extracted during processing; 6% mineral matter (MM), 57–74% non-nitrogen extract (NNE); 7–8% crude fiber; 25–41% NDF; 14% of acid detergent fiber (ADF); 1% lignin, 0.2% starch, 22–25% pectin; 3.88 mg vitamin C/100 g by-product, 1.6–1.8% calcium and low phosphorus content (0.08–0.75%) [74, 78, 79].

Pectin consists of a structural carbohydrate, a component of the soluble fiber fraction, which in turn is a polymer of galacturonic acid [80]. According to Muller and Prado [77], co-products with a high concentration of pectin have great potential for use in ruminant nutrition, as it presents high energy density, in addition to favorable fermentation, without the production of lactic acid, which maintains adequate conditions for ruminal functioning.

Because it contains an extremely low starch content, citrus pulp can favor ruminal pH, preventing a sharp decrease during digestion, which can cause metabolic disturbances, in addition to providing maximum cellulolytic activity and a higher acetate:propionate ratio [64, 81–85].

In a study conducted by Oliveira et al. [34] evaluating three supplements, one mineral, one corn-based protein-energy supplement and the other based on citrus pulp, the authors concluded that citrus pulp as an energy source in supplements provided at 0.3% of body weight (BW) can be used in the supplementation of Nellore bulls during the rainy season, without compromising forage intake and fiber digestibility, improving ruminal microbial efficiency.

#### *2.4.2 Dried distiller's grain (DDG)*

Protein ingredients in the diet are usually considered the costliest. Thus, the search for alternatives that reduce production costs and even that do not generate competition with food consumed by humans in livestock systems has been increasingly intensified.

An alternative protein ingredient is dried distillers' grain with soluble (DDGs), a co-product of ethanol from corn or sorghum production, which has been gaining attention in animal nutrition for meeting the energy and protein demands of diets in pasture or feedlot systems [71]. In Brazil, however, most industries produce DDG without soluble, resulting from dry milling of corn processing for ethanol production [66]. DDG is typically characterized by its high protein content with low ruminal degradation, presenting between 50 and 62% of RUP in its composition, responsible for the greater supply of MP to the ruminant [86]. Comparatively, the RUP content of DDG is higher than that of cotton and soybean meal, 50 and 20%, respectively [87].

Chemical composition of DDG, however, varies depending on the type, variety and quality of grains, soil conditions, fertilization, irrigation, production and harvesting methods, in addition to factors related to processing in distilleries [88].

Tjardes & Wright [89] demonstrate variations in the nutritional characteristics of DDGs, ranging from 88 to 90% in DM content, 25 to 32% of CP, 43 to 53% in RDP, 47 to 57% in RUP, 39 to 45% of NDF, 8.8 to 12.4% of lipids and 85 to 90% of TDN in studies conducted with beef cattle. Furthermore, the co-product contains highly fermentable fiber and low starch content, which reduces the risk of acidosis in cattle consuming a high-grain diet, improving rumen health, in addition to being a source of minerals [90]. According to Fonseca et al. [86], in Brazil, the DDG produced by most companies does not have the reconstitution of the soluble fraction, presenting lower values of EE and non-fibrous carbohydrates.

In a study of Buckner et al. [91], the authors tested the inclusion of up to 40% of DDGs in the total DM diet and observed that the inclusion of the co-product resulted in higher ADG compared to the control diet. Other studies that evaluated the use of corn DDG at levels of 0; 50 and 100% replacement for conventional protein sources (cotton meal and soybean meal) reported that DDG can 100% replace the protein source during the rearing phase on tropical pastures without any adverse effects on ADG, enteric CH4 emissions or N excretion [66, 92]. Furthermore, Hoffmann et al. [93] reported that the use of DDG does not affect animal performance finished in pasture or conventional feedlot, emphasizing that it is a viable alternative to replace conventional supplements in a tropical environment.

However, although DDG has the potential to replace conventional protein sources, its inclusion is limited mainly due to seasonal availability. In addition, unlike Brazil, countries such as the United States in some plants, use sulfuric acid for acidic starch hydrolysis during the processing of DDGs and for cleaning equipment, the excess of which can cause negative environmental impacts and even on the carcass quality [94, 95].

Other alternatives of agroindustry co-products that have been used in ruminant supplementation involve corn gluten, glycerin, and peanut crop residues, such as skin and husks.

#### **2.5 Feed additives**

In recent decades, the excessive use of antibiotics in animal production has resulted in a considerable increase in resistant bacteria, making it difficult to treat infectious animal diseases and compromising food safety [22]. These compounds are traditionally known as additives, which are defined as "substances intentionally added to feed, with the purpose of preserving, intensifying or modifying its properties, as long as it does not harm its nutritive value, such as antibiotics, dyes, preservatives, antioxidants among others" [96]. In general, additives are used to increase feed efficiency and animal performance, and are divided into different types, including ionophores, antimicrobials/antibiotics, microbial additives, organic acids, and plant extracts such as tannins, saponins and essential oils [97].

Ionophores are the most researched additives in ruminant diets, especially sodium monensin, and its use started in 1976 in beef cattle diets in the United States [98]. The action of ionophores in the rumen occurs through changes in the microbial population, selecting gram-negative bacteria that produce succinic and propionic acids or that ferment lactic acid, and inhibiting gram-positive bacteria that produce acetic, butyric, lactic and hydrogen (H2) acids, precursor of enteric CH4 production [98]. Due to this mechanism of action, the use of ionophores in ruminants can optimize energy metabolism, changing the proportion of volatile fatty acids (VFA) produced in the rumen and reducing CH4 production, as well as improving N metabolism by ruminal microorganisms, decreasing the absorption of NH3 and increasing the

*Advances in Pasture Management and Animal Nutrition to Optimize Beef Cattle Production… DOI: http://dx.doi.org/10.5772/intechopen.99687*

amount of protein that reaches the small intestine, in addition to reducing disorders arising from abnormal fermentation in the rumen, such as ruminal acidosis, bloat and coccidiosis [99].

Antibiotic additives have been used to promote growth for over 55 years, helping to reduce the cost of animal production. However, due to food safety, there are few antibiotics approved by agencies in different countries around the world [22]. The main products used include virginiamycin, bacitracin, flavomycin and tyrosine. In general, antibiotics act directly on rumen metabolism, as they modify the microbial rumen population to optimize ruminal fermentation and nutrient conservation, promoting antibacterial activity on gram-positive bacteria, activity against fungi and protozoa. Furthermore, antibiotics modify the ruminal digestibility of feed, reduce N degradation and enteric CH4 production, and can control subclinical diseases by suppressing infectious bacteria [100].

Microbial additives are composed of live cells of microorganisms and/or their metabolites, including yeasts, fibrolytic enzymes and probiotics, especially *Aspergillus orizae, Sacchariomyces cerevisae* and *Lactobacillus ssp*, and their use has increased because they are "natural" substances that promote growth to improve production efficiency in ruminants [101]. In general, microbial additives act in the production of antimicrobial compounds (acids, bacteriocins, antibiotics), prevent the establishment of unwanted microorganisms, reestablish the microflora of the digestive tract, and also improve immunity and stimulate animal growth [101]. Furthermore, the use of fibrolytic enzymes can stimulate endogenous ruminal activity and increase the rate and extent of forage digestion by ruminants, due to the improvement in the colonization of feed particles [102].

According to Carro & Ungerfeld [103], organic acids are an alternative to antibiotics and in ruminant nutrition, the most used as additives include malic, fumaric, aspartate, citric, succinic, and pyruvic. As they do not produce detectable residues in meat, the use of organic acids does not cause risks to food safety, however their cost is high. In the rumen, these additives can favor the use of lactate and prevent a sharp drop in pH, preventing ruminal acidosis, and reduce the production of enteric CH4.

As an alternative to antibiotics, many plants and plant extracts have received attention for their ability to manipulate ruminal fermentation and animal metabolism, in order to increase performance and promote beneficial effects to the environment [13]. Natural compounds commonly used in ruminant nutrition include condensed tannins, saponins and essential oils.

Condensed tannins (CT) are complexes composed of polyphenols, found in tropical legumes and other C3 plants, which bind to proteins, metal ions and polysaccharides, such as starch, cellulose, and hemicellulose [104]. When they exceed 6% of DM in the diet, CT are considered antinutritional factors because they reduce intake, fiber digestibility and animal performance, however in adequate doses (2–4% DM), CT can promote beneficial effects, especially in the regarding GHG emissions by ruminants [105]. These compounds can reduce protein degradation in the rumen and reduce NH3 concentration along with less urinary N excretion [106]. Besides, CT can also reduce fiber fermentation in the rumen, which consequently reduces H2 and acetate formation, in addition to inhibiting the growth of methanogenic microorganisms, thus reducing the production of enteric CH4 [106, 107].

Saponins, in turn, are glycosides naturally present in some plants, such as *Medicago sativa* (alfafa) and *B. decumbens* and are used in animal nutrition as growth inhibitors of ruminal protozoa and modulators of ruminal fermentation in cattle [108]. Essential oils, on the other hand, comprise secondary metabolites of some plants, responsible

for their odor and color, and are obtained by vaporization or distillation in water. According to Stevanović et al. [109], among the main essential oils, the most used are thymol present in thyme (*Thymus vulgaris*), oregano (*Origanum vulgaris*), limonene extracted from citrus pulp and guaiacol extracted from guaiac resin or clove oil from India. As a mechanism of action, these oils reduce the rate of deamination of amino acids, the rate of NH3 production, with an increase in the ruminal escape of N into the intestine. Furthermore, it can increase the concentration of total VFA without affecting other fermentation parameters and even inhibit methanogenesis.

In the context of organic additives, the Fator P (Premix®, Patrocinio Paulista, Brazil) was designed and developed using 100% natural and national technology, being formed by a complex combination of amino acids, probiotics, and essential fatty acids, such as omega 3 and omega 6, in addition to organic minerals and surfactants. The use of this additive in the diet of ruminants can improve fiber digestion, ruminal metabolism, nutrient absorption and, thus, animal performance, in addition to meeting new market trends, associating sustainability and profitability.

Several metabolic studies conducted using the Fator P in ruminant diet demonstrated greater stability and performance of animal metabolism, through better intake and absorption of fibrous feed and, mainly, in the energy availability from diet, which resulted in a 20% increase in weight gain [110–112]. Furthermore, the additive promotes improvements in carcass quality and milk composition, can benefit the female reproduction and the immune system, thus reducing costs with sanitary management. In the context of sustainability, the Fator P optimizes the dynamics of ruminal microorganisms which, associated with greater stability in ruminal fermentation, can reduce GHG emissions per arroba produced by up to 36%, in addition to not causing microbial resistance, and can be used without restrictions, as opposed to conventional additives [112].

The use of these organic additives, therefore, can help to fully exploit the genetic potential of animals and pastures and improve the efficiency of use, in addition to reducing environmental damage, especially with lower emissions of greenhouse gases. In a study evaluating the use of this additive, Leite et al. [113] reported that it increased DM intake of the animals during the initial phase in a feedlot system and did not change the performance, when compared to the conventional additive, monensin.

#### **3. Final considerations**

Although livestock is considered the villain of global warming, grazing and nutritional management strategies are essential to mitigate GHG emissions. Proper grazing management results in forage with a higher nutritive value, allowing for more efficient use of nutrients, which increases animal performance. The intensification of pasture use implies the adoption of diet supplementation at different times of the year, aiming to maximize the productive animal performance. Supplementation of beef cattle during rearing in rainy season is an effective strategy to intensify the system due to the period of efficient animal gain and pasture quality. The use of alternative additives to antibiotics can promote better productive responses, in addition to reducing enteric CH4 production and N2O emission by excreta. However, when adopting pasture management and supplementation techniques, it is necessary to assess the economic and environmental impacts.

*Advances in Pasture Management and Animal Nutrition to Optimize Beef Cattle Production… DOI: http://dx.doi.org/10.5772/intechopen.99687*

#### **Acknowledgements**

Financial support was provided by Premix® Company.

### **Conflict of interest**

The authors declare no conflict of interest.

### **Notes/thanks/other declarations**

The authors thank the members of UnespFor (Unesp Jaboticabal/SP Forage Team).

#### **Author details**

Andressa Scholz Berça1 \*, Eliéder Prates Romanzini1 , Abmael da Silva Cardoso1 , Luís Eduardo Ferreira2 , André Pastori D'Aurea2 , Lauriston Bertelli Fernandes2 and Ricardo Andrade Reis1

1 São Paulo State University, Jaboticabal, São Paulo, Brazil

2 Premix Company, Ribeirão Preto, São Paulo, Brazil

\*Address all correspondence to: dessaberca@yahoo.com.br

© 2021 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

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#### **Chapter 3**

## Potential Utilization of Insect Meal as Livestock Feed

*Sipho Moyo and Busani Moyo*

#### **Abstract**

Globally, the utilization of alternative protein sources in livestock feed has been extensively deliberated and established to be the best novel approach. Extensive research indicated that insects provide good opportunities as a sustainable, high quality, and low-cost component of animal feed. The use of insects in animal diet sounds to be the prospective opportunity leading to sustainability of animal feeds and meet the intensifying worldwide plea for livestock products. The value of these protein sources has, however, increased due to limited production, competition between humans and animals. The use of insects for feeding farmed animals represents a promising alternative because of the nutritional properties of insects and the possible environmental benefits, given the sustainability of this type of farming. Yet little has been documented about the nutrient composition of various insect meals, the impact of insect meal in the animal feed industry, safety, and attitude and willingness of farmers to accept insect-based animal feed and food. Therefore, this chapter seeks to document the potential utilization of insect meal as livestock feed.

**Keywords:** insect meal, safety, acceptance, chitin, benefits

#### **1. Introduction**

The Food and Agriculture Organization (FAO) emphasized the importance of alternatives to conventional animal feed due to limited amounts [1]. Currently, the core protein sources in monogastric animal diets are fishmeal, processed animal protein, milk by-product, soybean meal (SBM), rapeseed meal, and canola meal. The value of these protein sources has, however, increased due to limited production, competition between humans and animals [2]. In addition, Makkar et al. [3] stated that insects are good novel protein sources at a low-cost, with regard to their high nutritional value and low breeding space requirements. They are recommended as high quality, effective, ecological substitute sources of protein. More so, proteinenriched insects are another alternative reckoned to reduce the price of protein supplements in poultry diets. In addition, according to [4] insect components such as chitin, lauric acid, and antimicrobial peptides promote chicken health. Also, take into consideration that these insects can be utilized as a dried or fresh state in poultry diets [5]. Recently, scientists have started to study insects as state-of-the-art feed constituents for aquaculture [6, 7] and poultry [8, 9]. However, this chapter focuses on the

documentation of the proximate nutrient composition, impact on the animal feed industry, consumer acceptance, and safety of insect meal as animal feed.

#### **2. Chemical composition of different insect meals**

Insects at all stages of their lives are potentially rich in protein [8]. Frantic efforts by researchers have dealt with different insect species, as indicated in **Table 1**. The protein content of insect meals varies considerably, from around 39% up to 64.4% even when the meals are based on the same insect species. The nutrient concentration of insects depends on their life stage as well as the rearing conditions and the composition of the growth media used for insect production [3, 20].


**Table 1.**

*Summarized major chemical composition of different insect meals.*

#### **3. Impact of insect meal in the animal feed industry**

In general, insects can be utilized for human and animal feed because of their high nutritive value [21]. Several studies have indicated that insect meal can be utilized to substitute soybean and fish meal in animal diets [22–26]. This is because these are rich sources of macro and micronutrients [27]. For instance, the black soldier fly (BSF) *Hermetia illucens* larvae has a protein content of 37–63 g/100 g and fat levels of 20–40 g/100 g with balanced fatty acids and amino acids profiles [9, 28]. Furthermore, grasshoppers (*Ruspolia nitidula* Linnaeus) family *Tettigoniidae* contains 36–40 g/100 g crude protein, 41–43 g/100 g fat, 10–13 g/100 g dietary

fiber, and 2.6–3.9 g/100 g ash on a dry matter basis [29]. In addition, insects are excellent sources of minerals like potassium, calcium, iron, phosphorous, zinc, and magnesium and also vitamins covering riboflavin, thiamine, niacin, and vitamin B12 [30–32].

Furthermore, Onsongo et al. [24] reported that broiler chickens and quails fed on BSF larvae meal had a satisfactory taste, aroma, and nutritional composition of the meat. This denotes that BSF larval meal can be suitable to be incorporated in poultry diets. Also, insects have been fed to fish yielding good growth performance and feed conversion [33]. In addition, piglets fed with BSF larval meal exhibited good results on growth performance, with insignificant effects on blood profiles [26]. However, generally, the use of BSF larval meal has been proven to be an excellent constituent of animal feed [23–26].

High nutritional value, minimal space requirements, and low environmental impact combine to make insects an appealing option for animal feed [34]. Another major advantage is that insects are already used for the natural part of many animal diets [35]. Insect-based animal feeds are particularly attractive when considering the cost of standard feeds, currently accounting for 70% of livestock-production expenses [36].

The most promising, well-studied candidates for industrial feed production are black soldier flies, larvae, yellow mealworms, silkworms, grasshoppers, and termites [37]. Such previous research has revealed that insect meal can partially replace commercial soybean or fish meal in broiler feed, particularly as protein sources. In addition, Pretorius [38] reported that broiler chicken fed with housefly larvae increased their average daily gain, carcass weight, and total feed intake. More so, a recent study by [9] asserted that broilers fed on BSF meal improved their growth performance. With regards to nutritional value, insect diets improved meat products' taste. Also, Marono et al. [39] reported that laying hens fed on insect larvae meal exhibited no negative effect on feed intake, feed conversion efficiency, immune status, egg production, and health. Smallholder farmers in Asia and Africa frequently utilize insect diets on fish production [37]. Mealworms and housefly-larvae meal can substitute up to 40–80% and 75% of fishmeal in Nile tilapia/standard catfish (*Ameiurus melas* Raf.) diets without any detrimental effects, respectively [40, 41]. Replacing a fish meal with black-soldier-fly larvae meal in diets does not alter the odor, flavor, or texture of Atlantic salmon (*Salmo salar*) [42]. Another viable alternative to a fish meal is silkworm pupa, which was tested successfully for African catfish (*Clarias gariepinus*) fingerling diets [43]. More so, some other outcomes on insects to benefit the industry are presented in **Table 2**.



*DM, dry matter; CP, crude protein; BW, body weight; BWG, body weight gain; FCR, food conversion ratio; ADG, average daily gain; ADFI, average daily feed intake; AA, amino acids; AIA, apparent ileal digestibility; PUFA, polyunsaturated fatty acid.*

#### **Table 2.**

*Summary of effect of insect diet on growth performance of different animal species.*

#### **4. Consumer's acceptance of insect-based animal feeds**

The utilization of insect meal to replace unaffordable fish, animal, or plant protein ingredients in feeds is socially acceptable. This is because, naturally, fish and poultry are usually seen feeding on insects, for example, in the case of our free-range poultry

production systems [53, 57], which roam around in search of feed. More so, various insects have higher protein levels than conventional fish and soybean meals [58] and are comparable in performance with conventional protein sources when completely or partially replaced with fish protein in poultry diets [59]. With the fact that protein is the most costly ingredient in livestock diets, the use of insects sounds like a positive novel idea [60, 61].

The consumer's acceptance of meat products derived from animals-fed insects ought to be put into account. Before introducing insects as a new ingredient, it is necessary to establish the current perceptions of the targeted processors, traders, and poultry farmers. This is because farmers' perceptions of technology characteristics significantly affect their adoption decisions [62]. A few studies surveyed the consumer's readiness to buy animal products that originated from animals fed with insect meal [63, 64].

#### **5. Chitin content**

Chitin is a polysaccharide (linear polymer of β-(1–4)*N*-acetyl-glucosamine units) of the exoskeleton of arthropods [65]. However, chitin negatively affects the digestibility and nutritional traits of insects. In addition, it has been considered as indigestible fiber for the time in memorial. Chitin is the utmost form of fiber in insects [66], however, the nitrogen absence is also analyzed by the Kjeldahl method as a crude protein. It is, however, included in the nitrogen-to-protein conversion factor of 6.25, which overvalued protein content. For this reason, Janssen et al. [67] suggested a conversion factor of 5.60 ± 0.39. However, in some birds like chickens, the gastrointestinal tract (GIT) excretes the enzyme chitinase [68] which degrades chitin into its derivatives chitosan, chitooligosaccharides, and chitooligomers that are assimilated with easy into bloodstreams [68, 69]. Average chitin yields were 18.01 and 4.92% of dry weight from the exuvium and whole body of the *Tenebrio molitor* larvae [70]. The chitin composition depends on species and development stadium of the insect [66].

However, chitin has a positive effect on the operation of the immune system of poultry, which could reduce the use of antibiotics [1]. The prebiotic effect of chitin was observed by [71, 72] in increasing caecal production of butyric acid and [73] in improving the immune response of birds or due to reduction of albumin to globulin ratio [74]. In addition, chitin and its derivatives can aid to sustain a balanced and healthy GIT microbiota that keeps the amounts of potentially pathogenic bacteria (e.g., *Escherichia coli* and *Salmonella typhimurium*) low [75] and decreases the risk of intestinal diseases. By reducing the number of pathogenic microbiota, chitin encourages the proliferation of commensal bacteria. A positive effect of chitin was reported by [36] who also stated that a diet containing 3% of chitin decreased *E. coli* and *Salmonella* spp. in the 380 intestines. Chitin also has antifungal and antimicrobial properties [76].

#### **6. Nutrient digestibility**

Evaluating digestibility is a means to come up with an approximation of nutrient availability in a feed. In this regards, Woods et al. [77] reported that *H. illucens* larvae fed to quails have higher apparent digestibility for dry matter and organic matter to the control fed group. However, Bovera et al. [78] showed that the ileal digestibility coefficient of dry matter and organic matter in broiler fed *T. molitor* was lower by 2% than fed soybean diet. In addition, Cutrignelli et al. [79] reported reduced coefficients of the apparent ileal digestibility (AID) of dry and organic matter on laying hens fed *H. illucens* meal diet. These reductions were due to the strong decrease of the crude protein digestibility linked to the availability of chitin in the insect meals, which deleteriously influences the crude protein digestibility. However, no difference was observed between digestibility coefficients of the dry matter of *T. molitor* meal and *H. illucens* meal [80]. More so, Woods et al. [77] observed a higher apparent metabolizable energy for *H. illucens* larvae fed quail compared well to the control fed group. On similar results [81] did not find the differences among *T. molitor* oil and palm oil on AID of crude fat, and metabolizable energy. Furthermore, the apparent metabolizable energy of the *T. molitor* meal and *H. illucens* meal [80] was higher than all the ingredients mainly utilized in the poultry diet [39], substituted 500 g kg−1 of a maize meal-based diet with *M. domestica* larvae meal for 3-week old broiler chickens and detected a crude protein digestibility coefficient of 0.69. However, De-Marco et al. [80] detected no difference in the digestibility coefficient of the crude protein between *T. molitor* and *H. illucens*. In their study, Schiavone et al. [82] observed that there was no effect on apparent crude protein digestibility in chickens fed *T. molitor* oil as a total replacement for palm oil. Whilst, Bovera et al. [78] and Schiavone et al. [82] reported 8.2% and lower crude protein digestibility on chickens fed *T. molitor* larvae respectively, compared to soybean diet. De-Marco et al. [80], found that the (AID) of amino acids in the *T. molitor* meal was higher and showed less variation than in the *H. illucens* meal. According to the afore-mentioned results, insect meals can be an alternative crude protein source for soybean meals or fishmeal.

#### **7. Safety in utilization of insect meals**

Utilization of insects as constituents in livestock feed should consider safe due to the fact that they contain toxic substances secreted by the exocrine gland [83]. Just as in plants and animal feed, some insects are not safe to eat, they trigger allergic reactions. For instance, African silkworm (*Anaphe venata*) pupae have a thiaminase which causes thiamine deficiency [84]. In addition, *T. molitor* contains toxic benzoquinone compounds secreted by the defensive gland [85]. This benzoquinone is toxic to humans and animals, hence affecting cellular respiration resulting in kidney destruction, and has a carcinogenic effect [85]. However, insects may have antibiotic resistance genes [86] indicating that they can be filled with disease-causing organisms or mycotoxin from adulterated diets. More so, Wynants et al. [87] affirmed the contamination of wheat bran by the *Salmonella* spp. in *T. molitor* larvae. However, it is imperative to consistently monitor microbial pathogens of the substrate and the larvae in order to reduce pathogens in the *T. molitor*. Interestingly, Van Broekhoven et al. [88] reported that *T. molitor* larvae fed with diets contaminated with the mycotoxin deoxynivalenol were not affected in their growth and degraded the mycotoxin.

Besides, mycotoxins, insect feed can be contaminated with heavy metals, pesticides [89]. Mycotoxins from feed or substrate for insects rearing can negatively affect the growth, inhibit larval development or increase mortality of insects. More so, consumption of mycotoxin-contaminated insects can present a risk to animals. However, Schrogel et al. [90], reported no accumulation of mycotoxin in experiments fed with various insect species. Furthermore, Charlton et al. [91] reported that heavy metals accumulate in resultant insects. However, of the 1140 compounds measured, only seven were detected in the larvae, with Cd posing the greatest risk [91]. The *T. molitor* and *H. illucens* larvae consume feeds containing mycotoxins and pesticides,

the removal of these would render the resultant larvae free from toxins [92, 93]. More so, Purschke et al. [94] affirmed that there was no build-up of pesticides in BSF larvae raised on substrates spiked with pesticides. As a result, this renders it safe to be used in animal feed diets.

Some insects contain repellent or toxic chemicals, which they use as their defense mechanism. Grasshoppers spit brown juice as a means of defense while laybugs protect themselves from predators by releasing toxic fluid hemolymph. This yellowish fluid released from the leg joints is toxic in nature. Some insects are reported to transmit zoonotic agents such as bacteria, viruses, parasites, and fungi as vectors. According to [95] cases of botulism, parasites and food poisoning have been reported in using insect meal. In management, these health risks, proper processing, handling, and storage are a necessity in order to prevent contamination and spoilage. However, it is imperative to apply decontamination methods and shelf-life stability of insect meals in order to ensure and achieve marketability and food and feed safety.

#### **8. Production and availability of insect meal**

Insects have some valuable biological traits, which include being prolific, high feed conversion rate, and easy to raise with low feed cost [96]. According to [51] insects need less amount of feed for the production of 1 kg biomass, have higher fecundity, for instance, the common house cricket lays up to 1500 eggs over a period of about a month. Insect species are efficient feed converters as they are cold-blooded [51] and do not use energy to maintain body temperature [53]. Insects effectively utilize water and, in most cases, the feed is the main source of water [97]. Generally, the breeding of insects does not require complex infrastructure and their care is simple [98]. Insects propagation can be on several substrates, for example, cereals, decomposing organic materials, fruit or vegetables, poultry, pigs and cattle manure, industry by-products, or waste products, which would be environmental problems [51, 99]. According to [100, 101] utilization of insect meals or larvae meals can reduce the cost of poultry feed when nurtured on bio-waste. Insects can convert waste into valuable biomass [102] and convert low-quality plant waste into high-quality crude protein, fat, and energy in a short time [3]. Insects can effectively convert low-grade organic waste into high-quality protein. They utilize the organic waste, which could otherwise end up on dumpsites, causing environmental pollution. Insects have higher feed conversion efficiency. Most insects are produced on organic wastes or material that could not be consumed by humans. In their production, insects use minimal space, in the rearing process. Reports indicate that insects contribute less greenhouse gases than pigs and cattle [37].

The other benefit is the larvae's ability to decrease bacterial growth in the manure and thus reduce odor [97] *H. illucens* larvae has a 66% potential waste reduction and also waste reduction of 51–80% was recorded on pig, chicken, and kitchen waste [103]. Insect farming can also provide environmental benefits. Feeding waste materials to insects protects air, land, and water from potential contamination [104]. For example, the black soldier fly (*H. illucens* L.) (Diptera: Stratiomyidae), can be fed food waste that would typically be placed in landfills [105]. Accordingly, digestion of these materials suppresses noxious odors [105] greenhouse gases [106], and pathogens [107]. Furthermore, less land, water, and space are needed to produce insects, such as the black soldier fly, than traditional animal production [107]. Other benefits include fast development time (e.g., black soldier fly can develop to harvestable size

within 14 days) [108], versus beef (e.g., 12–18 months of feeding to reach the needed weight to slaughter) [109]. It is also worth noting that the full insect is edible unlike beef (48.5%) [36]. Because of the ability of the black soldier fly to consume a variety of organic wastes, while offering benefits to the environment, it is now viewed as the "crown jewel" of the insect.

Insects' growth rate depends on microclimate. The optimal temperature for most insect species rearing is 27–30°C [110]. The insect's larvae are the most effective for production and it is possible to produce more than 180 kg of live weight of *H. illucens* larvae in 42 days from 1 m2 [110]. The insect market for animal feed is continually increasing globally, especially focused on *T. molitor* larvae (mealworm). *T. molitor* and *H. illucens* (black soldier fly) are two of the most promising insect species for commercial exploitation and for use in poultry feeds [110] their production is seamless and well understood [111].

Even though raising insects seem to be a positive move, there is a dearth of information with regards to insect production methods and technologies, mainly in mass production [112–114]. This may be due to the fact that private companies hardly share that kind of information as they are in business. However, indigenous technical knowledge is mainly utilized in raising these insects, eventually becoming the basis of any technological improvement. For instance, in Indonesia, a complete guide on how *H. illucens* on medium-scale production has been circulated [115]. General, insect husbandry includes two main distinct units, which include the maintenance of the breeding colonies and the growing larvae [28]. In the event that business deals with adult insects, this requires more space for rearing purposes. As this implies to where crickets are raised [116]. Improved systems usually include an area to process insects and improve resultant products. Production wastes, like substrate remains and frass, may be utilized to come up with fertilizers in a devoted facility, hence leading to circularity and sustainability.

Insects can thrive in thickly populated areas, which permits mass production even in limited spaces. Generally, larvae and pupae are retained together with a nourishing substrate in small trays made of diverse materials like wood, highdensity polyethylene, or fiberglass. According to [116] trays for fattening *T. molitor* larvae are standard ones measuring 65 × 50 × 15 cm3 box, which are handled with ease and are deep enough to avert larvae or adults from fleeing. A recent study by Thevenot et al. [114] reported that a mill was designed to produce 17 tones of *T. molitor* annually with a density of 5 larvae cm−2.

Currently, insect raising is appealingly increasing awareness in developed countries, which are not enthusiastically normally involved in harvesting insects. This involves countries like Europe and the United States of America. As a result, promoting insect-based products to increase their market share. Indeed, insect husbandry linked with economic benefits produce food and feed ingredients that can benefit the developing and developed nations [117].

#### **9. Conclusion**

Insects pose an attractive opportunity to come up with novel sustainable protein source in monogastric animal diets taking into account their nutritive value, biosafety, and consumer acceptance. In addition, they also represent a means of converting food waste biomasses/streams into valued feed materials. However, it appears that there is nothing much barring us from utilizing insect meals as feed material. As a

*Potential Utilization of Insect Meal as Livestock Feed DOI: http://dx.doi.org/10.5772/intechopen.101766*

result, we need to get started and reduce the feed costs and also get rid of other insect limitations in their use as animal feed. Insect farming has great potential with regards to sustainably providing feed for the livestock. It can be concluded that insects can be an excellent alternative to partly replace soybean and fishmeal. However, further technological development of this sector and monitoring of the effects of these developments are needed. Also, further exploration is needed to assess the estimation equations parameters tied to these insect species.

#### **Acknowledgements**

The authors would like to extend their gratitude to Gwanda State University for granting us an opportunity, resources, facilities to work on this chapter. Our appreciation also goes to the Animal Feed Science and Nutrition-Health Environment for affording us the opportunity to make this contribution. This research did not receive any external funding from outside.

#### **Conflict of interest**

The authors declare no potential conflict of interest.

#### **Thanks**

Our appreciation also goes to the Animal Feed Science and Nutrition-Health Environment for affording us the opportunity to make this contribution.

#### **Author details**

Sipho Moyo\* and Busani Moyo Faculty of Life Science, Department of Animal Science, Gwanda State University, Filabusi Epoch Mine, Zimbabwe

\*Address all correspondence to: sipho.moyo@gsu.ac.zw

© 2022 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

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## Ruminal Microbiome Manipulation to Improve Fermentation Efficiency in Ruminants

*Yosra Ahmed Soltan and Amlan Kumar Patra*

#### **Abstract**

The rumen is an integrated dynamic microbial ecosystem composed of enormous populations of bacteria, protozoa, fungi, archaea, and bacteriophages. These microbes ferment feed organic matter consumed by ruminants to produce beneficial products such as microbial biomass and short-chain fatty acids, which form the major metabolic fuels for ruminants. The fermentation process also involves inefficient end product formation for both host animals and the environment, such as ammonia, methane, and carbon dioxide production. In typical conditions of ruminal fermentation, microbiota does not produce an optimal mixture of enzymes to maximize plant cell wall degradation or synthesize maximum microbial protein. Well-functioning rumen can be achieved through microbial manipulation by alteration of rumen microbiome composition to enhance specific beneficial fermentation pathways while minimizing or altering inefficient fermentation pathways. Therefore, manipulating ruminal fermentation is useful to improve feed conversion efficiency, animal productivity, and product quality. Understanding rumen microbial diversity and dynamics is crucial to maximize animal production efficiency and mitigate the emission of greenhouse gases from ruminants. This chapter discusses genetic and nongenetic rumen manipulation methods to achieve better rumen microbial fermentation including improvement of fibrolytic activity, inhibition of methanogenesis, prevention of acidosis, and balancing rumen ammonia concentration for optimal microbial protein synthesis.

**Keywords:** microbial manipulation, rumen, feed additives, phytochemicals, fiber degradation, microbial protein, acidosis

#### **1. Introduction**

Rumen inhabits several microbial populations, that is, bacteria, protozoa, fungi, bacteriophages, yeasts, and methanogens symbiotically, which are very dynamic, plastic, and redundant in function with the changes in diets though core microbiota persists, which has probably evolved by host-microbiota interaction in the evolutionary pressure over thousands of years [1]. A symbiotic relationship exists between rumen microbes and host animals in which both provide desirable substrates to

each other mainly through these ways—1) physical breakdown of feed particles by mastication and rumination expands their surface area for microbial attachment and degradation, and consequently, microbes secrete various enzymes for dietary substrate degradation, 2) ruminal movements bring microbes in contact with the dietary substrate by mixing of digesta and consequently produce fermentation products (e.g., H2, CO2, ammonia, short-chain fatty acids (SCFAs), and 3) utilization (absorption and consumption) of the fermentation products for keeping optimal ruminal conditions (e.g., pH) to maintain microbial growth and microbial protein synthesis [2]. Therefore, due to the interactive ecosystem of the rumen, any modification to one component of this system has several effects on other components. The fermentation end products of any diet are incorporated into the final animal products (meat or milk). Thus, manipulation of the ruminal fermentation pathways is the most effective approach to improve ruminant health and production efficiency without exaggerated increases in nutrient supply. This in particular should help the small livestock holders in developing countries for continued production.

The literature explored various manipulation strategies including enhancing or inhibiting the growth or the metabolic activity of specific rumen microbiota (e.g., archaea for methanogenesis) and/or altering the ruminal fermentation toward specific pathways (e.g, decreasing H2 production and increasing short-chain fatty acids (SCFAs) production [3, 4]. Extensive literature supports the supplementations of various rumen modifiers; however, efforts are still underway to find appropriate methods to simultaneously improve livestock production while reducing greenhouse effects on the environment. Through the following aspects, the most common methodologies for modifying the ruminal microbiome and fermentation characteristics are discussed in this chapter.

#### **2. Enhancing fibrolytic activity and short-chain fatty acid production**

Lignocellulose (complex polymers of cellulose, hemicellulose, pectin, and lignin) makes up the majority of the ruminant diet. Generally, forages, including crop residues, provide the main source of nutrition to ruminants that contribute to the food security and primary source of income of smallholder farmers in the developing countries [5–7]. This is also true where grazing animals are common in the developed countries. Hence, forage is virtually the only source of nutrition in the main beefproducing northern Australia, North and South America [8].

Although ruminants can digest fibrous feedstuffs, dietary cell wall polysaccharides are rarely completely degraded in the rumen. Less than 50% of the plant cell wall of most forage grasses are digested and utilized. This is attributed to the combination of the biochemical and physical barriers present in the ingested fibrous feedstuffs and retention time limitations of the ingested dietary substances in the rumen [9], resulting in excessive nutrient excretion, low nutrient intake, and a significant loss of dietary energy in the form of CH4 emission [10]. Therefore, enhancing the rumen microbiota to degrade plant cell walls usually leads to improve animal productivity.

Ruminants cannot degrade lignocellulose themselves. An involved community of fibrolytic microorganisms catalyzes the degradation of the plant cell walls in the rumen. The major classical fibrolytic bacteria involved in fiber degradation are *Fibrobacter succinogenes, Ruminococcus albus, Ruminococcus flavefaciens, Butyrivibrio,* and *Prevotella* spp. [11]. Anaerobic fungi also contribute to degrade cell wall components and play a special role in degrading low-quality forages. Fungi are able to

#### *Ruminal Microbiome Manipulation to Improve Fermentation Efficiency in Ruminants DOI: http://dx.doi.org/10.5772/intechopen.101582*

penetrate the plant tissue as a result of their filamentous growth and can degrade up to 34% of the lignin in plant tissues [12]. Fungi (i.e., *Neocallimastix* sp.) have a broad range of highly active fibrolytic enzymes and are the only known rumen microorganisms with exo-acting cellulose activity [11]. Cellulolytic activity is present in many rumen protozoa species, and the most efficient cellulose degraders are *Epidinium ecaudatum, Eudiplodinium maggii,* and *Ostracodinium dilobum* [13].

There are various well-established procedures that can be used to improve forage utilization including modifying ruminal microbial fermentation toward more fiber degradation. These include mechanical and chemical processing of forages and genetically engineering of plants for cell wall composition. However, we will focus on ruminal fibrolytic microorganisms and their products in the following sections of the chapter.

#### **2.1 Genetically engineered fiber-degrading bacteria**

The manipulation of genes in genetically engineered organisms can produce a product with novel specific characteristics that may have significant value. This concept was exploited in developing genetically modified fiber-degrading bacteria to optimize their activity by producing the correct mixture of fibrolytic enzymes to maximize plant cell wall degradation. *Ruminococcus* and *Fibrobacter* strains were the most targeted fiber-degrading bacteria for genetic modifications because they cannot produce exocellulases that are active against crystalline cellulose. Therefore, altering this activity would make them more potent [11]. The genome sequences of *F. succinogenes, R. albus,* and *Prevotella ruminicola* strains are available [11].

As early as 1995, Miyagi et al. [14] suggested that inoculation of genetically marked *R. albus* into a goat rumen might be of benefit to rumen function, but they found that the inoculant usually disappears from goat rumen after 14 days. One of the reasons for this is that bacteria reproduce within the physiological and ecological limits of the rumen ecosystem in which cooperative networks exist among ruminal microorganisms; since some organisms cleave specific bonds, others utilize particular substrates, while others produce inhibitors [11]. The scientists' sights were turned to *Butyrivibrio* species because they are among the most rumen bacteria capable of hemicellulose degradation and are regarded as being ecologically robust [15]. Gobius et al. [16] reported the successful transformation of a diverse range of eight strains of *Bu. fibrisolvens* with xylanase (family 10 glycosyl hydrolases) from rumen fungus *Neocallimastix patriciarum*. Glycosyl hydrolases family 10 was selected because it is different from family 11, which typically exists in *Bu. Fibrisolvens* and this family is characterized by high specific activity and resistance to proteolysis. The transformation was functionally successful and the *in vitro* fiber digestibility measurements revealed an improvement in plant fiber degradation by the recombinant xylanase; however, this still does not allow them to compete with the far more fibrolytic species *Fibrobacter* and *Ruminococcus* [11]. Another genetically engineered bacteria, *Bacteroides thetaiotaomicron* was inoculated at approximately 1% of the total population into *in vitro* dual-flow continuous culture fermenters and persisted for at least 144 h with relative abundances of 0.48–1.42% and increased fiber digestion, particularly hemicellulose fraction [17]. Generally, most of the experiments that used modified fibrolytic bacteria were *in vitro* trials. However, it should be taken into consideration that the *in vitro* fermenters did not express the full complement of rumen microorganisms (particularly protozoa). Moreover, this microbial manipulation application seems to be costly, especially for the small livestock holders in developing counties.

#### **2.2 Direct-fed microbials**

The concept of direct-fed microbials is different from the term probiotics. Probiotics were identified by any live microbial feed additive that may beneficially influence the host animals upon ingestion by improving microbial balance in the intestine [18]. Viable microbial communities, enzyme preparations, culture extracts, or combinations of those products were included in the concept of probiotic supplements [19]. The DFM has a narrower definition than probiotics as it is defined as a source of life, naturally occurring microorganisms alive, naturally occurring microorganisms that improve the digestive function of livestock. The DFM includes three main categories; bacterial, fungal, and a combination of both [20]. DFM must be alive to impact ruminal fermentation; thus, the viability and number of organisms fed must be ensured at the time of feeding. Lactic acid-producing and utilizing bacterial species of *Lactobacillus, Bifidobacterium, Streptococcus, Bacillus, Enterococcus, Propionibacterium*, *Megasphaera elsdenii* and *Prevotella bryantii,* and yeasts such as *Saccharomyces* and *Aspergillus* were the significant microbes of most of the DFM for livestock production [21].

DFM can grow under ruminal conditions and manipulate the microbial ecosystem. Various factors may affect the activity of DFM including microbial strains, time of feeding, feeding system, treatment period, physiological conditions, and dosages [20, 22]. The microbial strains seem to be the main influencer—DFM containing mainly lactic acid-producing and utilizing bacteria can manipulate the growth of microorganisms adapted to lactic acid in the rumen while preventing the drastic pH drops, for example, *M. elsdenii* [19]. DFM of *Propionibacterium* species can manipulate the fermentation pathways toward a more molar portion of propionate production [20, 23]. *Propionibacterium* is naturally found in high numbers in the rumen ecosystem and known to ferment lactate to propionate, providing more substrates for lactose synthesis in early lactation dairy cows, improving energy efficiency for the growing ruminants by reducing methane emission [20, 23].

Direct-fed microbials, based on fungal cultures, mainly contain *Saccharomyces cerevisiae* and *Aspergillus oryzae*, which can remove oxygen from the surfaces of freshly ingested feed particles to maintain the ruminal anaerobic conditions for the growth of cellulolytic bacteria [22, 24]. Moreover, the end metabolites of yeasts in the rumen can provide the ruminal microbiota with growth factors (i.e., rumen acetogens, digestive enzymes, anti-bacterial compounds, organic acids, and vitamins), resulting in stimulation of ruminal cellulolytic bacteria and maintenance of pH for optimal fiber degradation, and consequently greater production performance [21, 22]. Due to the low cost of DFM compared to other commercial feed additives, it can be included among the suitable solutions to manipulate the ruminal fiber degradation for the smallholder livestock sectors.

#### **2.3 Exogenous fibrolytic enzymes**

Products of exogenous fibrolytic enzymes (EFE) that contain primarily cellulolytic and xylanolytic activities can manipulate the ruminal fiber degradation, and improve feed conversion efficiency and thus lead to enhanced productive efficiency of ruminants [9]. Published literature suggests that the mode of actions of EFE products are likely different than that of DFM products. The activities introduced to the rumen by EFE are not novel to the ruminal ecosystem as they would act upon the same sites of the feed substrate particles as endogenous fibrolytic enzymes [25]. The

#### *Ruminal Microbiome Manipulation to Improve Fermentation Efficiency in Ruminants DOI: http://dx.doi.org/10.5772/intechopen.101582*

release of reducing sugars by EFE is probably an essential mechanism by which EFE operates [26]. The degree of sugar release is dependent on the substrate types as well as the type of enzymes. The released sugars can attract secondary ruminal microbial colonization, or remove barriers to the microbial attachment to substrate feed particles by cleaving the linkage between phenolic compounds and polysaccharides [9]. As a result, the most significant effects of EFE probably occur in the interval between the arrival of the feed particles into the rumen and its colonization by ruminal microorganisms, as only the rate, not the extent, of cell wall degradation, has been improved [25]. EFE can also manipulate the rumen fibrolytic microorganisms by enhancing their endogenous fibrolytic activities.

Genes from ruminal fungi encoding cellulases, xylanases, mannanases, and endoglucanases have been successfully isolated. Protein bioengineering has been employed to improve the catalytic activity and substrate diversity of fibrolytic enzymes from ruminants. This has resulted in fibrolytic enzymes with up to 10 times higher specific activity, pH and temperature optima, and enhanced fiber-substrate binding activity than the original enzymes [27]. This, together with the low manufacturing cost, has led to more recent developments in the enzyme production industry, and as a result, a wide range of commercial EFE products is now available. Frequently the manufactures' recommended doses of most commercial EFE products have been measured under wide ranges of pH (4.2–6.5) and temperatures (40–57°C), which are not always close to typical ruminal conditions. Moreover, most of the commercial EFE products for ruminants are often referred to as xylanases or cellulases. However, none of these products comprise single enzymes; secondary enzyme activities are invariably present, namely, proteases, amylases, or pectinases [9]. A wide variety of feed substrates can be targeted by a single EFE product. Thus, the random addition of these products to ruminant diets without consideration for specific rumen conditions (pH 6.0–6.5 and 39°C) and the not yet tested efficiency for specific substrate will result in unpredictable effects and thus discouraging the adoption of the EFE technology [28, 29].

In general, enhancing the rumen microbiota to degrade the dietary fibers through the above-discussed strategies may lead to accelerating the energy production in the forms of short-chain fatty acids (SCFAs) and/or microbial protein synthesis. At the same time, it may also produce high amounts of CO2 and CH4.

#### **3. Decreasing methanogenesis and increasing propionate production**

The ruminal fermentation is the primary source of CH4 emission from livestock; it is one of the most potent greenhouse gases featured by short atmospheric mean lifetime. Furthermore, a significant proportion of the ingested feed energy is also lost as CH4 [40]. Methane is produced by methanogens mainly by reduction of CO2 through the hydrogenotrophic pathway. Formic acid and methylamines produced by other ruminal bacteria are also reduced to CH4 by some methanogens. Therefore, methanogens interact with other ruminal microorganisms (e.g., protozoa, bacteria, and fungi) through interspecies H2 transfer [4]. Thus, maximizing metabolic H2 flow away from CH4 toward SCFAs production could improve production efficiency in ruminants and decrease environmental impact. There are various direct and indirect strategies to manipulate rumen methanogenesis; among these options, inhibiting the growth or the metabolic activity of methanogens seems to be the most effective approach. The efficiency of these strategies mainly depends on where methanogens reside. It can be seen from the smaller number of archaeal 16S rRNA gene sequences (461 vs. 8162)

recovered from protozoa than from ruminal content or fluid [4]. Free methanogens are mainly integrated into the biofilm on the surfaces of feed particles where H2-producing bacteria actively produce H2. These methanogens protected by the biofilm may not be inhibited to an extent similar to the free-living peers by anti-methanogenic inhibitors [4]. Also, methanogens can be inhibited indirectly through inhibiting rumen ciliate protozoa. Based on fluorescence *in situ* hybridization analysis, about 16% of the rumen ciliate protozoa contained methanogens inside their cells [30]. Most rumen ciliate protozoa have hydrogenosomes, unique membrane-bound organelles producing H2 by malate oxidization; therefore, these organelles can attract some species of methanogens as endosymbionts [4].

Methane formation pathways comprise of three main steps; transfer of methyl group to coenzyme M (CoM-SH), reduction of methyl-coenzyme M with coenzyme B (CoB-SH), and reusing heterodisulfide CoM-S-S-CoB [4, 31]. Thus, obstruction of any of these steps may manipulate CH4 production. A wealth of literature on rumen CH4 manipulation strategies in ruminants have been published recently, but relatively very few have emphasized the suitable mitigation strategies at the farm level [32]. Each method has some potential advantages and limitations. The principal interest for animal producers is income, as they usually do not take CH4 mitigation strategies or climate changes into account. Thus, any strategy to mitigate greenhouse gasses emission would only be of practical interest if achievements on the efficiency of animal production can be obtained. This can be obtained through rumen CH4 modifiers that enhance the production of SCFAs and/or reduce proteases. The following part addresses some of these microbial modifiers.

#### **3.1 Ionophores**

Ionophores are polyether antibiotics that act as inhibitors to hydrogen-producing bacteria. They are widely used as successful growth promoters in the livestock industry due to their ability to modulate rumen fermentation toward propionate production, thereby decreasing CH4 production. Since propionate and CH4 are terminal acceptors for metabolic H2, any increase in propionate production may accompany reduced CH4. In addition, ionophores positively affect ruminal fermentation through inhibition of deamination compared to proteolysis, inhibition of hydrolysis of triglycerides, and biohydrogenation of unsaturated fatty acids, while enhancing the trans-octadecenoic isomers (cited from [33]).

From the literature, monensin and lasalocid are the most well-known ionophoretype antimicrobials used as rumen modifiers. Mainly, they inhibit Gram-positive bacteria; however, they can also inhibit some Gram-negative bacteria. Ionophores decrease CH4 production by inhibiting H2 producing bacteria by penetrating the bacterial cell wall membrane. They act as H<sup>+</sup> /Na+ and H+ /K+ antiporters, dissipating ion gradients required for the synthesis of ATP, transport of nutrients, and other essential cellular activities in bacteria, resulting in retardation of cell growth and cell death [4, 34]. Monensin can decrease total methanogens number in cattle, and also alter the community composition of methanogen species, for example, monensin decreased the population of *Methanomicrobium* spp. while increasing that of *Methanobrevibacters* spp. [4].

Unfortunately, ionophores present a temporary impact on ruminal manipulation effects due to the adaptation of the microorganisms of these inhibitors. Ionophores are now restricted due to the possible resistance of pathogenic microorganisms to antibiotics [33]. Recently, the global scenario has shifted the interest toward plant

*Ruminal Microbiome Manipulation to Improve Fermentation Efficiency in Ruminants DOI: http://dx.doi.org/10.5772/intechopen.101582*

natural feed additives with potential abilities to modulate CH4 emission [35, 36]. Moreover, the type of the dietary feeds affects the efficiency of ionophores with the better effect of ionophores observed in high starch diets [33]. Thus, this approach seems to be less effective for the small livestock holders in most developing countries since the forages are the main ingredient in the diets.

#### **3.2 Natural feed additives as rumen modifiers**

#### *3.2.1 Plant secondary compounds*

Numerous plant secondary compounds (PSC), including tannins, flavonoids, saponins, essential oils (EOs), organosulfur compounds, have been recognized as having the potential to modulate ruminal microbial fermentation [37–39]. Plant secondary compounds are natural phytochemicals with the potential ability to manipulate rumen fermentation without causing microbial resistance or residual noxious effects on animal products [3]. Unlike ionophores, the different active components found in plant extracts may manipulate ruminal microbiota through more potent mechanisms of action (e.g., antimicrobial and antioxidant), which may avoid the risk of losing activity over time [40].

#### *3.2.2 Tannins*

Tannins are polyphenolic compounds with different molecular weights ranging from 500 to 5000 Da [41]. Tannins are classified into two major groups, that is, condensed (CT) and hydrolyzable tannins (HT). CT are proanthocyanidins consisting of oligomers or polymers of flavan-3-ol subunits. They act through binding with dietary proteins and carbohydrates by making strong complexes at ruminal pH [41–43]. Therefore, they are the most plant secondary metabolites studied in terms of rumen modulation pathways.

The literature reported quite various effects of CT supplementations regarding CH4 mitigation [38]. Some studies suggest a direct effect of CT on methanogens by binding with the proteinaceous adhesin or parts of the cell envelope, which impairs the establishment of methanogens-protozoa complex and decreases interspecies H2 transfer, and inhibits growth [44]. Other studies suggest an indirect effect of CT through the anti-protozoal effect. However, the effects of CT on rumen protozoal activity are varied in the literature, probably because some of the CTs have a direct effect on rumen methanogenic archaea, which are not associated with the protozoa. Tannins also can indirectly inhibit CH4 per unit of the animal product through tannin–protein or organic matter complexes under ruminal conditions, while protein from these complexes is released post ruminally, making it available for gastric digestion at abomasum and small intestine conditions, leading to enhancing the animal productivity [43]. Another theory is that tannins can act as H2 sink reducing the availability of H2 for CO2 reduction to CH4, implying that 1.2 mol CH4 is produced per mol of catechin [44].

Tree foliages are good feed resources for the small ruminants, which are rich in protein and perform catalytic functions in improving ruminal fermentation, especially in low-quality forage-based diets in developing countries [45]. The nutritionists have paid great attention to the tanniferous legumes and tree foliages as alternative cheap feed resources (especially in drought conditions and arid and semi-arid regions) and to achieve CH4 mitigation goals in the developing countries [46]. Many plants were investigated in the literature; however, the results are highly variable

among studies. Soltan et al. [43] studied various tanniniferous browsers and found that some plants (i.e., *Prosopis* and *Leucaena*) similarly modulate ruminal fermentation as ionophores perform by decreasing the acetate to propionate ratio, CH4 and NH3-N, while *Acacia* reduced CH4 through decreasing fiber degradation although it had similar CT concentration as *Leucaena*. Thus, it seems that not only does tannin concentration play a role in the modulation of the ruminal fermentation process, but also types, molecular weights are important in determining tannin potency in modulating rumen fermentation patterns. The presence of HT and other plant secondary metabolites (mimosine in *Leucaena*) together with CT can interact with the action of CT [44, 47].

#### *3.2.3 Saponins*

Saponins are a group of plant secondary metabolites with high molecular weight glycosides in which a sugar is linked to a hydrophobic aglycone. It can be generally classified as steroidal and triterpenoid [48, 49]. The effects of saponins on rumen fermentation modulation have been reviewed extensively [49]. The main biological effect of saponins is on the cell membranes of bacteria and protozoa. Saponins are highly toxic to protozoa compared with bacteria because saponins can form complexes with sterols present in the protozoal membrane surface, disrupting the membrane function [49]. Thus, it can indirectly affect the methanogenic archaea through their symbiotic relationship with rumen protozoa [38]. However, some literature assumed that the effects of saponins on rumen protozoa could be transient due to the ability of ruminal bacteria to degrade saponins into sapogenins. The sapogenin compound cannot affect protozoa [50].

#### *3.2.4 Essential oils*

Essential oils (EO) are volatile aromatic complexes obtained from different plant volatile fractions by steam distillation. They can be obtained from various plant parts including leaf, stem, fruit, root, seed, flower, bark, and petal. EO contains numerous bioactive substances; the most important ones are terpenoids (monoterpenoids and sesquiterpenoids) and phenylpropanoids. Due to the lipophilic properties of these components, EO act against various rumen bacteria through interacting with the cell membrane [3].

Several EO compounds, either in pure form or in mixtures, had antioxidant and anti-bacterial properties; therefore, they can modulate the ruminal fermentation pathways [51]. The EO, unlike ionophores, does not alter the ruminal microbial activities through a specific mode of action. Therefore, EO may have more potent mechanisms of action that may not likely lose their effectiveness over time. Soltan et al. [40] suggested two mechanisms in explaining how combination of phenylpropanes and terpene hydrocarbons components in EO mixtures work together to enhance additive antimicrobial activity—1) phenolic compounds may increase cell membrane permeability through the action of hydroxyl group, thus facilitating the transport of terpene hydrocarbons into the microbial cells, which then combine with proteins and enzymes inside the cells; 2) phenolic compounds could increase the size, number or duration of the existence of the pores created by the binding of terpene hydrocarbons with proteins in cell membranes.

The effects of EO on rumen fermentation are variable depending on concentrations, types, diet and adaptation period, but most EO are found to have anti-methanogenic

#### *Ruminal Microbiome Manipulation to Improve Fermentation Efficiency in Ruminants DOI: http://dx.doi.org/10.5772/intechopen.101582*

properties [35, 52]. Patra and Yu [52] studied various EO with different chemical structures (clove, eucalyptus, origanum, peppermint, and garlic oil) *in vitro* at three different concentrations (0.25, 0.50, and 1.0 g/L) for their effect on CH4 production and archaeal abundance and diversity and they found that all these EO suppressed CH4 production, but the extent of CH4 inhibition and ruminal fermentation differed among the EO. Further studies are needed to understand the interactions of the active compounds with the dietary ingredients and their activity against specific methanogens should be identified without adverse effects on fermentation patterns and rumen fiber degradability, as well as the different doses for each EO. Also, attention needs to be paid to the palatability as some EO may adversely affect palatability and dry matter intake due to the aroma they add to the ration. Therefore, many products of encapsulated EO are available in commercial forms, but this raises the question of the suitability of these products as feed additives at the farm level in developing countries.

#### *3.2.5 Propolis*

Propolis is a mixture of resinous substances collected from buds of deciduous trees and crevices in the bark of coniferous and deciduous trees and secretions by honeybees [53, 54]. The bees use propolis to fill cracks, cover hive walls and embalm invading intruder insects or small animals [55, 56]. The literature reported that the chemical composition of propolis is highly variable by bee collection site since geographical location plays an important role [54]. The most bioactive components are belonging to groups of isoflavones, flavonoids, and fatty acids that have been reported to be biologically active [53]. Recently, bee propolis has been recognized as a natural alternative feed additive to antibiotics in ruminant diets [54]. Compared to ionophores (e.g., monensin), different propolis sources can reduce CH4 production while improving the organic matter digestibility and total SCFAs *in vitro* and *in vivo* [53, 57]. Morsy et al. [58] reported that CH4 reduction caused by propolis supplementation is accompanied by increasing urinary allantoin, total purine derivatives, and enhancements of individual and total SCFAs. Thus, they suggested that propolis can help in the redirection of ruminal organic matter degradation from CH4 production to microbial synthesis and SCFAs. From a practical view, propolis can be a promising feed additive in the vegetation places where it is produced in a large amount such as Brazil.

#### **3.3 Plant oils**

Fats are usually used as energy sources for dairy cattle. The addition of fats is a promising approach for modulating rumen microbial communities and the fermentation process. Fats are known to inhibit microbial activity; however, supplementing fats up to 6% of dry matter has shown no adverse effects on total nutrient digestibility and total SCFAs [59]. A meta-analysis study suggests that methane emissions can be declined by 0.66 g/kg DM intake with each percentage increase in dietary fats, within dietary fat concentrations of 1.24–11.4% [59]. Fats containing high levels of C12:0, C18:3, and polyunsaturated fatty acids up to 6% of the dietary diet may be considered for CH4 mitigation without compromising the productivity in dairy cattle [59].

Plant oil supplements can modulate CH4 directly by inhibiting rumen protozoa and methanogens while enhancing biohydrogenation of polyunsaturated fatty acids (PUFA) to act as ruminal hydrogen sink for hydrogen produced by rumen microorganisms and reducing fiber degradation with less H2 production in the rumen [60].

The literature showed variable effects of plant oils on CH4 emission and rumen fermentation; this might be related to the oil type (free oil or whole seed), diet composition (forage to-concentrate ratio), and fatty acid type (short-chain or PUFA) present in diets [59]. Generally, consideration of vegetable oils supplementation to lower CH4 emission may depend upon the cost and expected outcome effect on animal productivity.

#### **3.4 Chitosan**

Chitosan is a natural polycationic polymer, nontoxic, biocompatible, biodegradable; thus, it is safe for human as well as animal consumption [61]. It is a linear polysaccharide composed of two repeated units—D-glucosamine and N-acetyl-Dglucosamine linked by β-(1–4)-linkages [61]. It can be found in the structural exoskeleton of insects, crustaceans, mollusks, cell walls of fungi, and certain algae, but it is mainly obtained from marine crustaceans [62]. It is characterized by anti-inflammatory, antitumor, antioxidative, anticholesterolemic, hemostatic, and analgesic effects. Moreover, it has a high antimicrobial affinity against a wide range of bacteria, fungi, and protozoa; therefore, it has been recently tested as a rumen fermentation modulator and considered as a promising natural agent with CH4 mitigating effects [61]. The antimicrobial mechanism of chitosan can include interactions at the cell surface and outer membranes through electrostatic forces, the replacement of Ca+2 and Mg+2 ions, the destabilization of the cell membrane, and leakage of intracellular substances, and cell death. The antimicrobial properties of chitosan can also include chelating capacity for various metal ions and the inhibition of mRNA and protein synthesis [61].

It seems chitosan activity depends on the diet type as well as the ruminal pH. The literature reports suggest that the maximum effect of chitosan is noted when grain (starch) is incorporated in the ration at low pH values, shifting the fermentation pattern to a more propionate production pathway, which could be explained by the higher sensitivity of Gram-positive bacteria than Gram-negative bacteria against chitosan [61, 63]. This type of change in ruminal fermentation by chitosan results in reductions in CH4 production. Moreover, supplementation of chitosan alters the rumen bacterial communities related to fatty acids biohydrogenation, that is, *Butyrivibrio* group and *Butyrivibrio proteoclasticus* that lead to increases in concentrations of milk unsaturated fatty acids and cis-9,trans-11 conjugated linoleic acid [64].

#### **3.5 Chemical feed additives**

Numerous chemical additives were used to modulate the rumen microbial activity for optimizing animal productivity, namely, defaunating agents, and anti-methanogenic agents to reduce CH4 emission. Patra et al. [4] reported the most promising antimethanogenic agents that effectively lower CH4 without adverse effects on rumen degradability or producing SCFAs and each of which works through different modes of action when added together to additively decrease CH4 production. These include halogenated sulfonated compounds (e.g., 2-bromoethanesulfonate, 2-chloroethanesulfonate, and 3-bromopropanesulfonate), 3-nitrooxypropanol (3NOP), nitrate, and ethyl-3NOP are used to inhibit methyl-CoM reductase activity, the final limiting step to complete the methanogenesis pathways. Halogenated aliphatic compounds with 1 or 2 carbons can impair the corrinoid enzymes function and inhibit cobamidedependent methyl group transfer in methanogenesis or may serve as terminal electron (e− ) acceptors. Some agents, namely, lovastatin and mevastatin were found to inhibit

3-hydroxy-3-methylglutaryl coenzyme, which is essential in the mevalonate pathway to form isoprenoid alcohols of methanogen cell membranes [4]. The addition of nitrate has two benefits—it can inhibit methanogenesis and acts as a nonprotein nitrogen source, which could be useful in low-quality base diets [65].

#### **4. Control of acidosis**

Diets containing high amounts of rapidly fermenting soluble carbohydrate result in pH drop due to excessive production of lactate or VFA or a combination of both, which may be of subacute ruminal acidosis (pH between 5.0 to 5.5) or acute acidosis (<5.0) type with acute or chronic in duration [66]. The consequences of acidosis range widely along with death and more importantly lower productivity, especially in subacute ruminal acidosis [66, 67]. Decreasing the ruminal pH leads to inhibition of rumen cellulolytic bacteria. Therefore, maintaining ruminal pH at the average level (5.8–7.2) is an essential factor to balance the rumen microorganisms between acid producers and consumers. In this context, buffering reagents and alkalizer (e.g., sodium bicarbonate, magnesium oxide, and calcium magnesium carbonate), direct-fed microbials, and malate supplementation may increase pH in the rumen and production when ruminants are fed with high-grain based diets [66, 68]. Malate supplementation can stimulate Selenomonas ruminantium that converts lactate to VFA [69]. Marden et al. [70] reported that the inclusion of 150 g of sodium bicarbonate increased total ruminal VFA concentration by 11.7% compared to the control diet fed to lactating cows. The addition of sodium bicarbonate, magnesium oxide, and calcium magnesium carbonate reduced the duration of time ruminal pH persisted below 5.8 in lactating dairy cows fed a high-starch (342 g/kg DM) containing diet and increased milk and fat yield, and milk fat concentration, but reduced milk *trans*-fatty acids isomers [71]. The efficacy of the acid-neutralizing capacity of the alkalizers depends upon physical and chemical properties that influence the solubility in the ruminal conditions. However, in developing country conditions, the acidosis problems are usually less severe as ruminants are mostly fed with roughage-based diets.

#### **5. Enhancing ruminal microbial protein synthesis**

Microbial protein in the rumen (RMP) accounts for between 50 and 90% of the protein entering into the duodenum and supplies the majority of the amino acids required for growth and milk protein synthesis [72]. Therefore, increasing RMP synthesis is important for improving animal productivity. Moreover, increasing the RMPS is an effective strategy to decrease protein (i.e., nitrogen) excretion in livestock since the dietary protein unless utilized properly by ruminal microorganisms is degraded to ammonia in the rumen, and ammonia is absorbed from the rumen, metabolized to urea in the liver, and excreted in urine causing environmental nitrogen pollution [10, 73].

There are many factors affecting RMP synthesis including dry matter intake, type of the ration fed (forage to concentrate ratio), the flow rate of digesta in the rumen, the sources, and synchronization of nitrogen and energy sources [74]. Among these, the amount of energy supplied to rumen microbes was found to be the main factor affecting the amount of nitrogen incorporated into RMP. Phosphorylation at the substrate level and electron transport level are two significant mechanisms of energy

generation within microbial cells [75]. Based on 10 reconstructed pathways associated with the energy metabolism in the ruminal microbiome, Lu et al. [75] found that the energy-rich diet increased the total abundance of substrate-level phosphorylation enzymes in the glucose fermentation and F-type ATPase of the electron transporter chain more than the protein-rich diet. Therefore, they concluded that energy intake induces higher RMP yield more than protein intake. In this context, any factor affecting the available amount of soluble carbohydrates to rumen microbes will affect the efficiencies of RMP synthesis. Therefore, most of the previously mentioned rumen modifiers (e.g., plant secondary metabolites, dietary oil) may affect the RMP synthesis; however, most of the studies have ignored the determination of RMP.

Maximizing RMP synthesis seems to be the most effective approach for the small livestock holders in most developing countries since microbial protein sometimes becomes the only protein source for the animals fed on poor quality forage diets with low or without concentrate supplementations. Balancing the diets of these animals by supplementing of leaves of legumes, urea-molasses multinutrient blocks, urea in the form of slow ammonia release, and other nonprotein nitrogen resources found to be favorable for RMP synthesis [8, 10, 29, 73]. It has been recognized that feeding high true proteins (the most expensive ingredients in the ruminant diet) can be utilized by ruminal bacteria in about the same way as the ammonia from nonprotein nitrogen (e.g., urea). The optimum concentrations of ammonia in the rumen for maximal RMP synthesis are about 50–60 mg/L and 27–133 mg/L from the *in vitro* and *in vivo* studies, respectively [73].

Reduction in CH4 production can enhance the RMP synthesis. Soltan et al. [10, 29] observed that inclusion of *Leucaena* in sheep diet up to 35% with or without polyethylene glycol enhanced the RMP and the body nitrogen retention while reducingCH4 emission; they suggested that optimizing microbial growth efficiency might help to redirect organic matter degraded from CH4 formation to RMP synthesis. Plants or feed additives containing phytochemicals with high antioxidant activity can promote more nutrients for microbial uptake, enhancing RMP synthesis, while reducing CH4 emission due to lessening the ruminal oxidative stress [36, 53].

#### **6. Reduction of ruminal protein degradation and ammonia production**

From an economic view, dietary protein concentrates increase production costs, especially for developing countries. Furthermore, the microbial population in the rumen has a high proteolytic capacity to degrade the dietary protein. Therefore, nutritionists are interested in formulating diets with ruminal undegradable protein sources. The protein degradation in rumen depends mainly on three processes—proteolysis, peptidolysis, and deamination. Many protein-degrading bacteria are naturally found under ruminal conditions, that is, *Ruminobacter amylophilus*, *P. ruminicola*, *Butyrivibrio fibrisolvens, S. ruminantium*, *Streptococcus bovis*, and *P. bryantii*. There are many amino acid-fermenting bacteria, that is, *Clostridium sticklandii*, *Clostridium aminophilum*, *M. elsdenii*, *B. fibrisolvens, P. ruminicola, S. bovis,* and *S. ruminantium* [73]. Increased ruminal ammonia concentration is an indicator of the high degradation of dietary protein. Many factors can affect ruminal protein degradation and ammonia concentration, such as the type of dietary protein, the energy sources, the predominant microbial population, the rumen passage rate, rumen pH [35]. The ruminal bacteria can utilize ammonia for the synthesis of amino acids required for their growth. The optimal ammonia concentration needed to maximize the RMP synthesis ranges from 88 to 133 mg/L [76].

#### *Ruminal Microbiome Manipulation to Improve Fermentation Efficiency in Ruminants DOI: http://dx.doi.org/10.5772/intechopen.101582*

Several inhibitors of ruminal microbial protein degradation and ammonia production were reported in the literature. Condensed tannins, slow-release urea products, encapsulated nitrate, clays (e.g., bentonite and zeolite that acts through cation exchange capacity), and biochar were found to reduce the rapid increase in ammonia production and maintained the ruminal pH. Urea pool in the rumen is contributed from urea in the diet and recycling of urea through saliva and ruminal wall. The urease enzyme produced by the ruminal microbiota rapidly degrades urea to ammonia causing ammonia toxicity and inefficient urea utilization when used in excessive amounts [73]. Inhibitors of urease may reduce the risk of ammonia toxicity and efficient utilization of urea and other nonprotein nitrogen compounds [77].

#### **7. Enhancing functional values of milk and meat**

Ruminant-derived foods (milk and meat) contain a high amount of saturated fatty acids, which are associated with human health concerns. Therefore, improving the functional value of ruminants' products by increasing the content of beneficial fatty acids (FAs) and decreasing detrimental ones, specifically, decreasing the content of saturated FAs and increasing n-3 FAs and conjugated linoleic acids (e.g., cis-9, trans-11 C18:2, also called rumenic acid) have been great interests among the researchers [78]. Manipulating ruminal biohydrogenation of polyunsaturated fatty acids (PUFAs) has been the target to increase meat and milk content of rumenic acid and vaccenic acid, as both compounds are major intermediates in the biohydrogenation. To elevate rumenic acid content in products, inhibiting the last step of biohydrogenation needs to be attempted without affecting lipolysis and isomerization and reduction of linoleic acid and linolenic acid to rumenic acid and vaccenic acid. Alternatively, to elevate PUFAs in meat and milk, in particular n-3FAs, inhibition of early steps of biohydogenation should be targeted. Secondary compounds such as tannins, saponins, or essential oils rich in terpenes present in plants and forages or supplementation of vegetable oil can improve some aspects of meat and milk quality including n-3 FAs, conjugated linoleic acids, antioxidant properties [73, 79–81].

#### **8. Conclusions**

The ruminal fermentation end products are typically the outputs of several interactive reactions among the rumen microbial populations. Manipulations of rumen microbial fermentation toward enhancing fiber digestibility, SCFAs production, and outflow of microbial biomass, while reducing ammonia and CH4 emission are the most probable ways to improve animal productivity. Numerous rumen fermentation modifiers have been studied during the last few decades; however, their positive effects are sometimes associated with undesirable effects or highly significant costs (e.g., ionophore antibiotics, anti-methanogenic chemical feed additives, or essential oils). Moreover, most of these modifiers exhibited inconsistent efficacy in the literature mainly because of the variability in animal age, breed, diet formulation, physiological status, rumen microbial resistance, and adaptation. Despite the long history of studies on the rumen modifiers, most of the measurements are determined through the treatment period but knowledge is still limited on animal responses in later life or impacts on human health and growth. However, there is unanimous agreement that an ample array of drought-tolerant plants containing effective bioactive compounds,

DFM, fibrolytic enzymes, and nonprotein nitrogen sources would cost-effectively modify the ruminal fermentation. Therefore, a combination of two or more of these rumen modifiers with complementary modes of action may be a promising approach to optimize the productivity of ruminants in developing countries.

### **Conflict of interest**

The authors declare no conflict of interest.

#### **Author details**

Yosra Ahmed Soltan1 and Amlan Kumar Patra<sup>2</sup> \*

1 Faculty of Agriculture, Department of Animal and Fish Production, Alexandria University, Alexandria, Egypt

2 Department of Animal Nutrition, West Bengal University of Animal and Fishery Sciences, Kolkata, India

\*Address all correspondence to: patra\_amlan@yahoo.com

© 2021 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

*Ruminal Microbiome Manipulation to Improve Fermentation Efficiency in Ruminants DOI: http://dx.doi.org/10.5772/intechopen.101582*

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Section 3 Environment

### **Chapter 5**
