**3. Challenge of replacing antibiotics with probiotics**

The recommendation for antibiotics to be replaced by other compounds has been the subject of discussions around the world, mainly after the European Community officially banned its total use in animal nutrition, with the disclosure of Regulation (EC) no. 1831/2003. The main reason for substitution is the occurrence of cross-resistance to drugs used to treat bacterial infections in humans [10]. According to the joint report by the World Health Organization (WHO), Food and Agriculture Organization (FAO) and World Animal Health Organization (OiE), there are still countries that do not yet have control over antibiotics that circulate in animal production (Africa and the Latin America). Many of them lack an organizational structure for control and others only limited their use to promote growth of the animals. Most of the European countries have adopted strict measures to control antibiotics that are circulating throughout the food chain and used in hospitals [9].

Following the recommendations of world health agencies, meat exporting countries, such as Brazil, for example, as the largest meat exporter in the world have been adapting to the demands of international markets. Through the prohibition of antimicrobials commonly used as growth promoters in animal production. Through the normative instructions (IN), the Brazilian Ministry of Agriculture and Livestock has implemented the ban on the following substances as a performanceenhancing zootechnical additive: Olaquindox (IN n°. 11, November 24, 2004), carbadox (IN n°. 35, November 14, 2005), spiramycin and erythromycin (IN n°. 14, May 17, 2012), colistin sulfate (IN n°. 45, November 22, 2016) [36], and the substances bacitracin, tylosin, lincomycin, virginiamycin and tylosin (IN n°. 171, December 13, 2018), [37]. The inhibition is mainly for the purpose of export according to the recipient's rules.

To overcome a challenge of antibiotics concerns for human and animal health, substantial research that investigated alternative increased exponentially. Compounds, such as herbal medicines, [38, 39] prebiotics [40], organic acids [41],

**149**

challenges [54].

*Probiotics as a Promising Additive in Broiler Feed: Advances and Limitations*

resulting in the selection of resistant strains can be more drastic [44].

symbiotics and probiotics [42] aiming to achieve results like that of antibiotics has been carried out. Economic and environmental impacts may occur with the ban of antibiotics according to [43], implying an increase in production costs of edible noble meat, increase in water consumption and in the production of excreta, as it was observed higher feed consumption and worsening feed conversion when no antibiotics are used. However, the impacts with the frequent use of antibiotics

No significant differences was observed for the performance characteristics in the period from 1 to 21 days in birds of the group of the zinc bacitracin antibiotic, when compared to the group of a probiotic composed of *Lactobacillus, Bifidobacterium bifidum, Streptococcus thermophilus,* and *E. faecium,* with better weight gain being observed for these two groups in relation to the group without the

Studies carried out with the strains *Lactobacillus* spp., *Bifidobacterium bifidum,* 

Supplementation with *Bacillus subtilis* probiotic strain reduces infectious agents, such as *Salmonella*, improving the intestinal digestive and absorptive efficiency, in which the probiotic is able to control the population and load of cecal *Salmonella*, being similar to the effect of the antibiotic enrofloxacin [49]. According to WHO (2016), salmonellosis is considered a disease that affects people worldwide, and that

Corroborating the research carried out by [51] in Brazil, that when assessing the prevalence of several *Salmonella* spp., serotypes in chicken carcasses and live chickens in slaughterhouses, found that 50% of establishments had a prevalence above that recommended by Ministry of Agriculture, Livestock and Supply (MAPA). The same authors evaluated the resistance of *Salmonella* spp*.* serotypes to two groups of antimicrobials, fluoroquinolones and beta-lactams, and observed that the strains were more resistant to beta-lactam antimicrobials, which demonstrates the risk in

Another study [52] showed that the use of probiotics, and probiotic combined with 1% garlic powder, was able to promote villi with good width and height in the small intestine and improvements in the performance of birds in the absence of antibiotics, although no improvement in feed intake has been observed. The antimicrobial characteristics of garlic combined with the probiotic reduce the microbial load that in response optimizes the absorption of nutrients in the small intestine. Although lower feed consumption is observed in some studies, the probiotic allows improvements in other characteristics of greater economic importance such as body weight and feed conversion [53]. Lower feed consumption can be influenced by factors such as heat stress and environments with greater health

Naturally, the beneficial microbiota that inhabits the intestines of broilers uses a competitive suppression mechanism (as shown in below **Figure 1**) to reduce the multiplication of others that are pathogenic, preventing damage to the mucosa by

*Streptococcus thermophilus* and *Enterococcus faecium* indicate the efficiency of probiotics against pathogenic microorganisms when compared to conventional antibiotics, being able to reduce colonization by *Salmonella enteritidis* in the intestinal segments [46], without changes in feed consumption and feed conversion [47]. The practices of biosecurity in production combined with the use of probiotics are the way to maintain production efficiency and quality of the final product in the

has some serotypes resistant to conventional antimicrobials [50].

the treatment of clinical conditions of salmonellosis in humans.

**4. Promoting growth mechanism by probiotics in broiler**

*DOI: http://dx.doi.org/10.5772/intechopen.97957*

addition of additives [45].

current scenario, [17, 48].

#### *Probiotics as a Promising Additive in Broiler Feed: Advances and Limitations DOI: http://dx.doi.org/10.5772/intechopen.97957*

*Advances in Poultry Nutrition Research*

in the digestive tract were also observed [21].

strongly recommended by these authors.

**3. Challenge of replacing antibiotics with probiotics**

clearly established.

microbiota [33]. Other studies, showed that nutritional effects where probiotics act by increasing fiber digestion in birds and enzymatic activity [34]. A competitive inhibiting effect, in which high amounts of Lactobacillus bacteria's produce organic acids that enable low pH in the crop that suppresses the colonization of pathogens

Testing different strains *(B. subtilis* DSM 32324*, B. subtilis* DSM 32325, and *B. amyloliquefaciens* DSM 25840*)* in isolation and in combination were showed that the tested strains had different abilities to degrade proteins and carbohydrates and inhibit the growth of *C. perfringens* in vitro. The in vivo results demonstrated that combined strains can act more efficiently than isolated strains on performance parameters as well as reducing mortality in birds challenged by *C. perfringens* [21]. Another study [35] used combined strains of *Bacillus licheniformis* and *Bacillus subtilis*, in order to investigate their effects and found that probiotic supplementation can increase profits if associated with dietary restriction. In addition to the feed efficiency, there was no influence on the carcass yield, the relative weights of the liver, gizzards, proventriculus, small intestine and bursa of fabricius, and the visible fat of the carcass was reduced. The association of probiotics with prebiotics was

There is a belief that multiple strains combined with prebiotics have a better effect than isolated strains. FAO reported [20] on the use of probiotics in animals states that the benefit of using more than one strain in the same product still not

The recommendation for antibiotics to be replaced by other compounds has been the subject of discussions around the world, mainly after the European Community officially banned its total use in animal nutrition, with the disclosure of Regulation (EC) no. 1831/2003. The main reason for substitution is the occurrence of cross-resistance to drugs used to treat bacterial infections in humans [10]. According to the joint report by the World Health Organization (WHO), Food and Agriculture Organization (FAO) and World Animal Health Organization (OiE), there are still countries that do not yet have control over antibiotics that circulate in animal production (Africa and the Latin America). Many of them lack an organizational structure for control and others only limited their use to promote growth of the animals. Most of the European countries have adopted strict measures to control antibiotics that are circulating throughout the food chain and used in hospitals [9]. Following the recommendations of world health agencies, meat exporting countries, such as Brazil, for example, as the largest meat exporter in the world have been adapting to the demands of international markets. Through the prohibition of antimicrobials commonly used as growth promoters in animal production. Through the normative instructions (IN), the Brazilian Ministry of Agriculture and Livestock has implemented the ban on the following substances as a performanceenhancing zootechnical additive: Olaquindox (IN n°. 11, November 24, 2004), carbadox (IN n°. 35, November 14, 2005), spiramycin and erythromycin (IN n°. 14, May 17, 2012), colistin sulfate (IN n°. 45, November 22, 2016) [36], and the substances bacitracin, tylosin, lincomycin, virginiamycin and tylosin (IN n°. 171, December 13, 2018), [37]. The inhibition is mainly for the purpose of export

To overcome a challenge of antibiotics concerns for human and animal health, substantial research that investigated alternative increased exponentially. Compounds, such as herbal medicines, [38, 39] prebiotics [40], organic acids [41],

**148**

according to the recipient's rules.

symbiotics and probiotics [42] aiming to achieve results like that of antibiotics has been carried out. Economic and environmental impacts may occur with the ban of antibiotics according to [43], implying an increase in production costs of edible noble meat, increase in water consumption and in the production of excreta, as it was observed higher feed consumption and worsening feed conversion when no antibiotics are used. However, the impacts with the frequent use of antibiotics resulting in the selection of resistant strains can be more drastic [44].

No significant differences was observed for the performance characteristics in the period from 1 to 21 days in birds of the group of the zinc bacitracin antibiotic, when compared to the group of a probiotic composed of *Lactobacillus, Bifidobacterium bifidum, Streptococcus thermophilus,* and *E. faecium,* with better weight gain being observed for these two groups in relation to the group without the addition of additives [45].

Studies carried out with the strains *Lactobacillus* spp., *Bifidobacterium bifidum, Streptococcus thermophilus* and *Enterococcus faecium* indicate the efficiency of probiotics against pathogenic microorganisms when compared to conventional antibiotics, being able to reduce colonization by *Salmonella enteritidis* in the intestinal segments [46], without changes in feed consumption and feed conversion [47]. The practices of biosecurity in production combined with the use of probiotics are the way to maintain production efficiency and quality of the final product in the current scenario, [17, 48].

Supplementation with *Bacillus subtilis* probiotic strain reduces infectious agents, such as *Salmonella*, improving the intestinal digestive and absorptive efficiency, in which the probiotic is able to control the population and load of cecal *Salmonella*, being similar to the effect of the antibiotic enrofloxacin [49]. According to WHO (2016), salmonellosis is considered a disease that affects people worldwide, and that has some serotypes resistant to conventional antimicrobials [50].

Corroborating the research carried out by [51] in Brazil, that when assessing the prevalence of several *Salmonella* spp., serotypes in chicken carcasses and live chickens in slaughterhouses, found that 50% of establishments had a prevalence above that recommended by Ministry of Agriculture, Livestock and Supply (MAPA). The same authors evaluated the resistance of *Salmonella* spp*.* serotypes to two groups of antimicrobials, fluoroquinolones and beta-lactams, and observed that the strains were more resistant to beta-lactam antimicrobials, which demonstrates the risk in the treatment of clinical conditions of salmonellosis in humans.

Another study [52] showed that the use of probiotics, and probiotic combined with 1% garlic powder, was able to promote villi with good width and height in the small intestine and improvements in the performance of birds in the absence of antibiotics, although no improvement in feed intake has been observed. The antimicrobial characteristics of garlic combined with the probiotic reduce the microbial load that in response optimizes the absorption of nutrients in the small intestine.

Although lower feed consumption is observed in some studies, the probiotic allows improvements in other characteristics of greater economic importance such as body weight and feed conversion [53]. Lower feed consumption can be influenced by factors such as heat stress and environments with greater health challenges [54].

### **4. Promoting growth mechanism by probiotics in broiler**

Naturally, the beneficial microbiota that inhabits the intestines of broilers uses a competitive suppression mechanism (as shown in below **Figure 1**) to reduce the multiplication of others that are pathogenic, preventing damage to the mucosa by

**Figure 1.** *Possible mechanisms of performance promotion by probiotics.*

irritating toxins, controlling enteritis, and guaranteeing protection to the mucosa [5]. Mechanisms are described according to which microorganisms (1) competes for the site of adherence in the mucosa, for better use of nutrients and greater reproduction, in which the one in greater quantity will serve as a barrier that restricts the adherence of others in lesser quantity, reducing possibilities of the latter to multiply; (2) there is the production of organic acids that lead to a reduction in the pH of the medium and the establishment of an acidity that eliminate or decreases all intolerant microbiota, the majority of which are pathogenic; and (3) there is an activation of the immune response by the receptors (toll-like) present in the wall of beneficial bacteria, which, when in contact with the cells of the intestinal mucosa stimulate them to produce immunoglobulins, that will inhibit the multiplication of the pathogenic microbiota [18].

In environments where chickens are subjected to heat stress, probiotics in association with trace minerals, can help maintain or even improve performance parameters, resulting from the increase in the surface area of the intestinal villi [55].

The authors [56] found that the use of probiotics improves blood biochemical parameters, reduced serum uric acid concentration, modified intestinal microstructures and reduced enterobacteria in the ileum and cecum.

Probiotics in combination with other natural additives helps to make better use of the nutrients of alternative ingredients, which for the most part, have antinutritional factors, enabling the best use of these for the production of animal feed [57]. [58] concluded that broilers fed 15% of shea butter cake flour added to probiotics, obtained better carcass characteristics and noble cuts when compared to the control diet without probiotics and without flour.

Probiotics act in the restoration of intestinal microflora, decreasing inflammatory processes caused by pathogenic bacteria, with an increase in villus height, and improving zootechnical performance characteristics [59]. This effect was achieved due to competitive exclusion, reduction of enterotoxins and direct antagonism [60]. Other work also show that the use of probiotic improves the body weight and feed conversion of birds, when observing the increase in the levels of glucose and

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*Probiotics as a Promising Additive in Broiler Feed: Advances and Limitations*

albumin in the blood, which indicates better digestion and absorption of nutrients. The same authors suggest that studies must be carried out to investigate the ideal

The modes of action of probiotics are generally not understood. When summarizing the advantages of using probiotics, one should emphasize their role in protecting animals against pathogens, increasing the immune response, reducing the need for antibiotic-based growth stimulants and high safety of these formulas [19], these factors all contribute to the greater use of nutrients by the bird and, consequently, to

The limitations surrounding the application of probiotics are several, however those inherent in the breeding environment are those described here, among which

The absence of a common pattern in the effect of probiotics and their probiotic potential is directly connected to particular species, not to the genus or species of a microorganism. Studies with *Bacillus subtilis*, analyzing from performance to

Using Probiotics based on *Bacillus subtilis*, bone growth in broilers under an episode of cyclic heating was induced, which was attributed to the inhibition of bone resorption, resulting from the negative regulation of circulating TNF-a and

In chickens challenged with *C. perfringens* tested strains of *Bacillus subtilis*, they showed no significant difference in the ability to degrade proteins and carbohydrates and inhibit the growth of *C. perfringens* in vitro, when compared to the control without probiotics, [21]. Already combined with *L. amiloquaficiences*, the results demonstrate the suitability of the combination of multi - strains of Bacillus

*Lactobacillus acidophilus*) in isolation, were not effective in controlling *E. coli* infection in broilers and did not lead to significant weight gain. In addition, 75% of the mortality was obtained in treatments with the application of these probiotics. The combination of these probiotics with flavonoids (Taraxacum) improved indicators

According to assessments made on the use of probiotics in animals by FAO the effects of probiotics seem to result from their interaction with the host. Such interaction is likely to define the mode of action of probiotics, which may be similar in different probiotics, or a specific strain may function through various mechanisms and several strains of probiotics have similar effects on the gastrointestinal

The stability of the probiotic in the storage time is one of the criteria of useful technology established to demand from formulators [66]. However, situations of inadequate handling or conservation after acquisition are more likely to happen and may result in inactivating their effect, and consequent absence the effect now

A study by Liang [64], showed that probiotics *(Bacillus subtilis* and

*DOI: http://dx.doi.org/10.5772/intechopen.97957*

concentration of probiotic in the feed [61].

**5. Limitations on the use of probiotics in broilers**

**5.1 Absence of a pattern in the effect of probiotics**

biochemistry parameters showed variable results [21, 24, 62–64].

a better performance.

are summarized below.

CTX, [32, 65].

of diarrhea [64].

microbial population [20].

**5.2 Post-marketing handling and conservation**

expected, since it is a live microorganism.

evaluated as an effective probiotic.

*Probiotics as a Promising Additive in Broiler Feed: Advances and Limitations DOI: http://dx.doi.org/10.5772/intechopen.97957*

*Advances in Poultry Nutrition Research*

pathogenic microbiota [18].

*Possible mechanisms of performance promotion by probiotics.*

villi [55].

**Figure 1.**

irritating toxins, controlling enteritis, and guaranteeing protection to the mucosa [5]. Mechanisms are described according to which microorganisms (1) competes for the site of adherence in the mucosa, for better use of nutrients and greater reproduction, in which the one in greater quantity will serve as a barrier that restricts the adherence of others in lesser quantity, reducing possibilities of the latter to multiply; (2) there is the production of organic acids that lead to a reduction in the pH of the medium and the establishment of an acidity that eliminate or decreases all intolerant microbiota, the majority of which are pathogenic; and (3) there is an activation of the immune response by the receptors (toll-like) present in the wall of beneficial bacteria, which, when in contact with the cells of the intestinal mucosa stimulate them to produce immunoglobulins, that will inhibit the multiplication of the

In environments where chickens are subjected to heat stress, probiotics in association with trace minerals, can help maintain or even improve performance parameters, resulting from the increase in the surface area of the intestinal

The authors [56] found that the use of probiotics improves blood biochemical parameters, reduced serum uric acid concentration, modified intestinal microstruc-

Probiotics in combination with other natural additives helps to make better use

Probiotics act in the restoration of intestinal microflora, decreasing inflammatory processes caused by pathogenic bacteria, with an increase in villus height, and improving zootechnical performance characteristics [59]. This effect was achieved due to competitive exclusion, reduction of enterotoxins and direct antagonism [60]. Other work also show that the use of probiotic improves the body weight and feed conversion of birds, when observing the increase in the levels of glucose and

of the nutrients of alternative ingredients, which for the most part, have antinutritional factors, enabling the best use of these for the production of animal feed [57]. [58] concluded that broilers fed 15% of shea butter cake flour added to probiotics, obtained better carcass characteristics and noble cuts when compared

tures and reduced enterobacteria in the ileum and cecum.

to the control diet without probiotics and without flour.

**150**

albumin in the blood, which indicates better digestion and absorption of nutrients. The same authors suggest that studies must be carried out to investigate the ideal concentration of probiotic in the feed [61].

The modes of action of probiotics are generally not understood. When summarizing the advantages of using probiotics, one should emphasize their role in protecting animals against pathogens, increasing the immune response, reducing the need for antibiotic-based growth stimulants and high safety of these formulas [19], these factors all contribute to the greater use of nutrients by the bird and, consequently, to a better performance.
