**2. Types of prebiotics used in the poultry industry**

It is difficult to describe in a few words what a prebiotic is; nevertheless, all definitions agree that these compounds, when administered as feed ingredients, are

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*Use of Prebiotics as an Alternative to Antibiotic Growth Promoters in the Poultry Industry*

resistant to enzymatic digestion and cannot be absorbed, and still they confer a health benefit for the host animal by selectively stimulating the growth, metabolism, and composition of beneficial native bacteria in the GIT and eliminating the pathogenic ones [25–27]. In general, prebiotics share these common properties, but there are some others that are also common among them, including resistance to gastric acidity, selective fermentability by a limited number of potentially beneficial microorganisms, alteration of the GIT microbiota toward a healthier composition, and modula-

Although only carbohydrate-based compounds, such as nondigestible oligosaccharides and non-starch polysaccharides, were previously considered as prebiotic candidates, nowadays the prebiotic concept has expanded to "a substrate that is selectively utilized by host microorganisms conferring a health benefit," so that other substances might fit to it, including a diversity of oligosaccharides with varying carbon chain lengths and even polyphenols and polyunsaturated fatty acids converted to respective conjugated fatty acids [29, 30]. However, to confirm its status as a prebiotic, studies for each candidate must be performed in the target animal species for its intended use, demonstrating its beneficial health effects mediated

In aviculture, a wide range of prebiotic alternatives have been evaluated, trying to improve the GIT health and resistance against pathogen colonization; nevertheless, all of them have been well characterized, indicating their source, purity, chemical composition and structure, suitable dose, and side effects, and have the status of generally recognized as safe (GRAS). The most commonly used prebiotics in poultry diets are nondigestible oligosaccharides (NDO), including fructooligosaccharides (FOS) and inulin type, mannan oligosaccharides (MOS), xylooligosaccharides (XOS), galactooligosaccharides (GOS), and isomaltooligosaccharide (IMO), as well as some structural carbohydrate components of non-starch polysaccharides (NSP), such as β-glucan [25, 31, 32]. These prebiotics are commonly administered to poultry orally at first hours or days after hatching, either spraying them directly in the feed or by their direct addition in drinking water; but recently, the administration of in ovo prebiotics in chicken embryos has been proposed as a better route of delivery, since the doses of prebiotics used in ovo could be at least 10 times lower than after hatching, with the same beneficial effects as the

As mentioned above, the main purpose of prebiotics is to modify the intestinal microbiota in a favorable manner for the host animal and induce positive effects, not only in the intestinal environment but also systemically, which is reflected in positive improvements of the productive parameters such as egg production, body weight gain, feed conversion ratio, and mortality index [34–36]. Besides improved host health and productivity, prebiotics have also proven their efficacy to reduce colonization of important pathogens both for poultry production and public health, such as *Salmonella*, *Campylobacter*, *C. perfringens*, and *E. coli* [37–41]. This set of beneficial effects, along with the lower risks of undesirable side effects in the host and the fact that they are cheaper and easier to produce in a large scale than probiotics, make prebiotics an excellent option as an alternative to minimize the use of antibiotics in poultry production, thus contributing to reduce the problem of AMR [42, 43].

There are many mechanisms and functions of prebiotics which have been associated with the poultry GIT microbiota, and it seems that there are several bacteria involved in their use; but there is evidence that other microbiota-independent

*DOI: http://dx.doi.org/10.5772/intechopen.89053*

tion of the host animal defense system [28].

through the microbiota.

oral administration [23, 33].

**3. Mechanisms of action of prebiotics in poultry**

#### *Use of Prebiotics as an Alternative to Antibiotic Growth Promoters in the Poultry Industry DOI: http://dx.doi.org/10.5772/intechopen.89053*

resistant to enzymatic digestion and cannot be absorbed, and still they confer a health benefit for the host animal by selectively stimulating the growth, metabolism, and composition of beneficial native bacteria in the GIT and eliminating the pathogenic ones [25–27]. In general, prebiotics share these common properties, but there are some others that are also common among them, including resistance to gastric acidity, selective fermentability by a limited number of potentially beneficial microorganisms, alteration of the GIT microbiota toward a healthier composition, and modulation of the host animal defense system [28].

Although only carbohydrate-based compounds, such as nondigestible oligosaccharides and non-starch polysaccharides, were previously considered as prebiotic candidates, nowadays the prebiotic concept has expanded to "a substrate that is selectively utilized by host microorganisms conferring a health benefit," so that other substances might fit to it, including a diversity of oligosaccharides with varying carbon chain lengths and even polyphenols and polyunsaturated fatty acids converted to respective conjugated fatty acids [29, 30]. However, to confirm its status as a prebiotic, studies for each candidate must be performed in the target animal species for its intended use, demonstrating its beneficial health effects mediated through the microbiota.

In aviculture, a wide range of prebiotic alternatives have been evaluated, trying to improve the GIT health and resistance against pathogen colonization; nevertheless, all of them have been well characterized, indicating their source, purity, chemical composition and structure, suitable dose, and side effects, and have the status of generally recognized as safe (GRAS). The most commonly used prebiotics in poultry diets are nondigestible oligosaccharides (NDO), including fructooligosaccharides (FOS) and inulin type, mannan oligosaccharides (MOS), xylooligosaccharides (XOS), galactooligosaccharides (GOS), and isomaltooligosaccharide (IMO), as well as some structural carbohydrate components of non-starch polysaccharides (NSP), such as β-glucan [25, 31, 32]. These prebiotics are commonly administered to poultry orally at first hours or days after hatching, either spraying them directly in the feed or by their direct addition in drinking water; but recently, the administration of in ovo prebiotics in chicken embryos has been proposed as a better route of delivery, since the doses of prebiotics used in ovo could be at least 10 times lower than after hatching, with the same beneficial effects as the oral administration [23, 33].

As mentioned above, the main purpose of prebiotics is to modify the intestinal microbiota in a favorable manner for the host animal and induce positive effects, not only in the intestinal environment but also systemically, which is reflected in positive improvements of the productive parameters such as egg production, body weight gain, feed conversion ratio, and mortality index [34–36]. Besides improved host health and productivity, prebiotics have also proven their efficacy to reduce colonization of important pathogens both for poultry production and public health, such as *Salmonella*, *Campylobacter*, *C. perfringens*, and *E. coli* [37–41]. This set of beneficial effects, along with the lower risks of undesirable side effects in the host and the fact that they are cheaper and easier to produce in a large scale than probiotics, make prebiotics an excellent option as an alternative to minimize the use of antibiotics in poultry production, thus contributing to reduce the problem of AMR [42, 43].
