**3.11. Spoilage and fungal contamination**

showed potential to inhibit proteolysis that draws interest to improve animal forage quality through greater N utilization [63]. The mechanism for PPO protection of plant protein in the rumen is a consequence of complexing plant protein, rather than protease deactivation, and these complexed proteins reduce protein digestibility in the rumen and subsequently increase undegraded dietary protein flow to the intestine. It catalyzes the conversion of phenols to quinones, which are extremely reactive and bind with cellular nucleophiles such as proteins to form protein-bound phenols. Red clover and cocks foot (*Dactylis glomerata*) showed high PPO activity compared to other forages [64]. There are several reports on the positive effect of PPO on preserving polyunsaturated FA (PUFA) within rumen simulation models [17] and limiting post-harvest proteolysis [64, 65]. The effect of PPO on inhibition of ruminal proteolysis and biohydrogenation is reported at 25 and 11%, respectively [66]. Thus, the benefit of red clover silage is attributed to a reduction in lipolysis in silo and an increase in beneficial C18 PUFA in animal products. A number of factors, e.g. cultivar, growing season, stage of maturity, sward management including forage conservation method and cell damage, play a role in the extent

Ensiling TMR allows preservation and saves labor at the farm as it saves daily preparation cost of TMR with succulent fodder. This concept of silage making is aimed at ascertaining nutritional adequacy to livestock for maintenance and/or production. Production of TMR silage and feeding to production stock in a livestock farm are gaining rapid acceptability. However, the fermentation process of the substrates during ensiling may influence various nutritional components, and therefore, the loss should be kept minimum for easy adoption and maximize nutrient utilization efficiency. Balancing CP and total carbohydrates content with respect to concentration of fermentable N and sugars would provide a desired reducing environment for anaerobic degradation to lactic acid and rapid drop in pH. Brewer's grains are found to be a suitable by-product for ensiling as it improved aerobic stability when ensiled with various feeds as a TMR [67]. Five different silage types with cassava by-products (peel and pulp at different ratio) (40%) with corn husk (42%), Brewer's grain (14%) and molasses (3%) were evaluated and recommended as a useful energy source in Thailand during the dry period [54].

It is a key factor in ensuring that silage provides well-preserved nutrients to the animal with minimal amounts of mold spores and toxins. When silage is exposed to air on opening the silo, fermentation acids and other substrates are oxidized by aerobic bacteria, yeasts and

**i. Biochemical and microbiological factors**: Development of yeasts and molds during plant growth and during field wilting or storage and concentration of undissociated ace-

**ii. Physical and management factors**: Silage density and porosity are key physical factors

get for potential silage aerobic stability is generally 7 days including the time in the feed

into the silage mass during the feed-out period. A tar-

molds, and the stability is thus dependent principally on following factors [68]:

of enzyme activity.

**3.9. Total mixed ration (TMR) silage**

26 Ruminants - The Husbandry, Economic and Health Aspects

**3.10. Aerobic stability of silage**

tic acid in silage.

that affect the rate of ingress of O<sup>2</sup>

The epiphytic microbial populations are the starter culture and the survival and activity of these populations are also among the factors influenced by the characteristics of the crop at the time of ensiling and often contribute to spoilage and could be a potential health risk. Therefore, the types of LAB rather than the total numbers of bacteria present in the epiphytic populations may be more important in determining the efficiency of the fermentation process. Manuring onto forage prior to ensiling increases numbers of epiphytic enterobacteria (e.g. *Bacillus* and *Clostridium* spp.) and contact of the forage with soil can also increase yeast and mold counts in the silage [69]. Although these microorganisms are usually inactivated during ensiling, they can become active and contribute to accelerated spoilage when the silage is exposed to air upon feeding. Well-preserved silages are dependent on appropriate fermentation after storage, which results in low pH and production of sufficient acid to inhibit the growth of undesirable microorganisms. Lactate-oxidizing yeasts are generally responsible for the initiation of aerobic spoilage, and the secondary aerobic spoilage flora consists of molds, bacilli, listeria and enterobacteria [70]. The activity of harmful microorganisms not only reduces the silage quality (e.g. formation of butyric acid) but also increases the losses of energy and DM [71]. Hexoses are fermented to carbon dioxide and hydrogen, and subsequent decarboxylation and deamination of amino acids by these bacteria contribute to a decrease in the quality and quantity of forage. Yeasts also ferment sugars to ethanol and carbon dioxide with higher fermentation losses. Spoilage after opening the silage pit or bags seems to be concurrent problems faced by many farmers because LAB typically reduces the concentration of acetate, which is strongly antifungal, and increases concentration of lactate, which is a growth substrate for spoilage yeasts [6]. When silage is exposed to air during storage or at feeding, aerobic spoilage leads to increase in pH and losses of DM and nutrients [72] due to lactic acid degradation by mainly the lactic acid-utilizing yeasts (e.g. *Pichia*, *Candida*) [73]. Difference in anaerobic degradation of cereal and legume forages during silage making leaves more residual WSC than do legume silages, which is a readily available source of energy for the animal. But, upon exposure to air, these WSC are readily utilized by spoilage microorganisms and often become more prone to aerobic deterioration than legume silage.

Growth of spoilage fungi in baled silage is not of random occurrence but is facilitated where in-bale environments allow the fungi to survive, colonize and reproduce. Visible fungal growth was observed on baled grass silage during the winter feeding season [74]. The factors analyzed are the concentrations of ethanol and lactic acid, DM content, bale tying, month of bale feed-out, age of bales, polythene film damage, ryegrass dominance, bale storage location and volatile FA concentrations. Besides, the environmental factors inside the silo, e.g. moisture content, pH, acid and gas composition, are likely to influence the species composition of the fungal population and the extent to which mold colonization occurs. Oxygen ingress causes excessive moisture or dryness, condensation, heating, leakage of rainwater and insect infestation of the silo, leading to undesirable growth of microaerobic acid-tolerant fungi, which may lead to mycotoxins production in this substrate [75]. Mycotoxin-producing molds, Bacillus sps and *Listeria monocytogenes* in aerobically deteriorated silage form a serious risk to the quality and safety of milk and to animal health. An average of 32% positive cases observed with most frequent fungal species from *Aspergillus, Penicillium* and *Fusarium* in pre- and postfermented sorghum silage samples [76]. Thus, periodic monitoring is essential to prevent the occurrence of mycotoxicosis particularly in countries with hot and humid climates.

additives [6, 83–85]. Dual-purpose inoculants containing both homo and heterofermentative LAB have recently been developed and the beneficial effects on aerobic stability have been reported [86]. Some isolates of *L. buchneri*, besides producing acetic acid can produce ferulateesterase enzyme, which hydrolyses feruloyl ester linkages between lignin and hemicellulose, and thus advocated to potentially improve fiber digestibility of forages during ensiling [87]. The diversity of LAB species inhabiting silages stabilizes its fermentation quality and supports preservation. LAB inoculants (viz. *L. plantarum*, *L. rhamnosus*, *L. acidophilus*, *Pediococcus acidilactici*, *P. pentosaceus*, *Enterococcus faecium*, *Lactococcus lactis*, etc.) are safe and easy to apply,

non-corrosive, do not pollute the environment and are regarded as natural products.

Phytochemicals have antimicrobial properties against *E. coli*. The use of a high-quality PSMcontaining forage may have the dual benefit of being a good-quality forage and reducing *E. coli* shedding [88]. Significant potential to use plants rich in bioactive compounds (saponin and tannin) for enhancing animal health and productivity that include reproductive efficiency, milk and meat quality improvement, foam production/bloat control, methane production [89] and Nematode control [90] has now been realized. The physicochemical structure and concentration of the phenolic compounds in the diet modulate the beneficial effects, and therefore, conceptualization of producing "therapeutic silage" involving forages rich in desired bioactive components would harness clinical and health benefits, besides modifying

Rapid breakdown of herbage proteins in the rumen and inefficient incorporation of herbage N by the rumen microbial population are major determinants of N (and C) loss and pollution in pasture-based livestock production system. Thus, when livestock are given fresh forages, they can waste 25–40% of the forage protein-N during ruminal fermentation. An increase from 23 to 34% in rumen N use efficiency through feeding higher WSC containing grasses could result in a

than the yield from grass forages [92]. Shifting the animals from grass to legume plant species tends to decrease the enteric emission due to lower proportion structural carbohydrates and faster rate of passage which shifts the fermentation pattern towards higher propionate production. Further, enhancing N use efficiency in the rumen may also contribute to a reduction in the

address these concerns and enable eco-friendly livestock production. The impact of the form of C relative to N and the effect at different C:N ratios in terms of rumen function and conversion

efficiency is an area of considerable promise that requires further detailed research.

emissions [91]. Similarly, increasing the digestibility of cell walls

yield from the ruminal fermentation of legume forages is generally lower

production in ruminants tends to increase with maturity of

) excreted. The concept of mixed or TMR silage may certainly

losses, but in fresh grass and grass silage, the scope

Silage for Climate Resilient Small Ruminant Production http://dx.doi.org/10.5772/intechopen.74667 29

**3.12. Therapeutic silage**

30% reduction in N<sup>2</sup>

forage fed, and CH4

amount of C (both as CO<sup>2</sup>

the yield and quality of meat and milk.

O and NH<sup>3</sup>

and CH4

in forages has been practiced to lower CH4

of this approach seems limited. CH4

**4. Protecting environment: green livestock production**

#### *3.11.1. Controlling spoilage*

Addition of high levels of propionic acid is effective against aerobic spoilage, but its use has been restricted because of its corrosive nature, relative expensiveness, involvement in VFI depression and variable sensitivities of yeast [77]. Control of silage fermentation by microorganisms seems to be a safe and inexpensive alternative, and in this line, LAB inoculation has been recommended to improve the aerobic stability of silage [8]. Killer yeasts (e.g*. Kluyveromyces lactis*) are known to secrete a killer protein that is lethal to specific yeasts (e.g. *Saccharomyces cerevisiae*) in a model of silage fermentation [78]. Genetically modified killer strain of *K. lactis* constructed to avoid dependence on substrates of lactose/lactic acid, a principal product of silage fermentation, which reduced aerobic spoilage.

#### *3.11.2. Microbial inoculants*

The mechanisms by which the inoculants alter silage fermentation and potentially improve animal performance are numerous. It supports accelerated post-ensiling decline in pH enabling quality silage production, improves stability and DM preservation, conserves nutrients, enhances aerobic stability and improves voluntary intake, nutrient utilization and efficiency of production. There may be increase in lactic/acetic acid ratio and reduction in proteolysis and protein deamination, thereby allowing better utilization of WSC and increase in DM recovery [79]. The problem of aerobic instability could be prevented by the use of microbial inoculant *L. buchneri*, a heterofermentative LAB, which could improve the aerobic stability of silages through the production of acetic acid from lactic acid during the anaerobic phase of silage conservation [71, 80, 81]. The natural populations of LAB in fresh crops are often heterofermentative and low in number, and thus homofermentative bacteria are used as inoculants to improve silage preservation. This accelerates the initial phase of the fermentation process via anaerobic degradation of WSC into lactic acid with a rapid decrease in pH and thereby preventing growth of spoilage microbes, molds and other contaminants and supporting preservation and storage without further deterioration in quality. Usually, selected homofermentative LAB have been used to improve the efficiency of the fermentation process to minimize DM and nutrient losses over conservation [82]. To prevent the aerobic deterioration of silage, heterofermentative LAB species, such as *L. brevis* and *L. buchneri*, have been developed as silage additives [6, 83–85]. Dual-purpose inoculants containing both homo and heterofermentative LAB have recently been developed and the beneficial effects on aerobic stability have been reported [86]. Some isolates of *L. buchneri*, besides producing acetic acid can produce ferulateesterase enzyme, which hydrolyses feruloyl ester linkages between lignin and hemicellulose, and thus advocated to potentially improve fiber digestibility of forages during ensiling [87]. The diversity of LAB species inhabiting silages stabilizes its fermentation quality and supports preservation. LAB inoculants (viz. *L. plantarum*, *L. rhamnosus*, *L. acidophilus*, *Pediococcus acidilactici*, *P. pentosaceus*, *Enterococcus faecium*, *Lactococcus lactis*, etc.) are safe and easy to apply, non-corrosive, do not pollute the environment and are regarded as natural products.
