Prebiotics as feed additives in poultry


Prebiotics are defined as a non-digestible food ingredient that affects the host beneficially by selectively stimulating the growth and/or activity of one or a limited number of bacteria in the colon. In other words, prebiotics provide substrate for beneficial microbes of gastrointestinal tract (GIT). Large population of bacteria prevailing monogastric small intestine are potentially capable of utilizing the indigestible carbohydrate sources for energy. Recently, several studies have been conducted to manipulate beneficial bacteria in GIT and the use of prebiotics is a promising approach for enhancing the role of endogenous beneficial organisms in the gut. These can be also be used as potential alternatives to growth promoting antibiotics.


Prebiotics are food ingredients, which include non-digestible carbohydrate (oligo and polysaccharides) (Table 1). Oligosaccharides include lactose, lactulose, raffinose, stachyose, fructo-gluco and mannan-oligosaccharides; whereas, non-starch polysaccharides contain pectin, cellulose, hemicellulose, xylans and guar gum. Some peptides, proteins and certain lipids (both ester and ether) along with yeast also act as prebiotics. Lactose (glucouse + galactose) acts as a prebiotic in poultry due to lack of lactase enzyme in them. On the other hand, probiotics are live microorganisms which, when administered in adequate amounts, exhibit a health benefits on the host, including: regulation of bacterial homeostasis, stabilization of gastrointestinal barrier function, expression of bacteriocins, immunomodulatory effects (Gaggìa et al., 2010). Recently, different prebiotics and their synergistic combinations with probiotics were tested in field and laboratory trials such as a commercial prebiotic (Poulystar® by biomin, DN (DiNovo®, BioAtlantis Ltd, Tralee, Co., Kerry, Ireland) a Laminaria spp. seaweed extract containing laminarin and fucoidan, and BI (Bi2tos, Clasado Ltd, Sliema, Malta) a nondigestive trans-galactooligosaccharides (GOS) from milk lactose digested with Bifidobacterium bifidum (NCIMB 41171 b) different symbiotic preparations (SYN1: BI + Lactobacillus salivarius; SYN2: RFO + Lactobacillus plantarum). Apart from in-feed and in-water supplementation, in-ovo feeding of both prebiotics and probiotics have gained more attention recently. In-ovo technology involves administration of a solution of a given substance directly to incubating eggs (Madej et al., 2015). The idea behind in-ovo supplementation is to provide food to animal as early as possible to combat the possible pathogens that would be colonized at hatching (Bednarczyk et al., 2016).


Table 1: Sources of prebiotics

Characteristics of ideal Prebiotics

Prebiotics should have known structure, which can be documented. They should be palatable as food ingredient with easier large- scale processing. They should selectively enrich and beneficially alter activities for one or a limited number of beneficial bacteria. But they should not be hydrolyzed or absorbed by host enzymes or tissues. Overall, they should beneficially alter luminal or systemic aspects of the host defence system.


Mechanism of action

Because of their chemical nature these compounds are not absorbed in the upper part of GIT. When enter into the caecum/colon, some serves as a substrate for the endogenous bacteria, thus directly provides the energy, metabolic substrates and essential micronutrients. They limit the pathogenic bacteria development either by acting on bacterial attachment or by competitive inhibition (possibly blocking lectins or intestinal receptors sites).Their role in immunomodulation is also very crucial (Fig 1).

Further their mechanism of action can be listed as:

1. Lowering the gut pH through lactic acid production (Gibson and Wang, 1994).

2. Inhibiting/preventing colonization of pathogens (Bengmark, 2001).

3. Modifying metabolic activity of normal intestinal flora.

4. Stimulation of immune system (Monsan and Paul,1995)


Previous work on prebiotics (broiler)

Piray et al. (2007) reported relative weight of breast and thigh to body weight were significantly (p<0.01) higher in Fermacto® fed broilers as compared to control group. (Fermacto® is a microbial feed supplement derived from Aspergillus Mycelium). Yang et al. (2009) stated that FOS improved broiler’s gain about 5-8% and improved feed conversion ratio by 2-6%. Yeast cell wall containing MOS reduced intestinal Salmonella concentrations by 26% in broiler chicks compared with chicks fed an unsupplemented diet. With MOS, improvement in weight gain and feed conversion in fattening chickens by up to 6%. (Spring et al., 2000).


Prebiotics like MOS, FOS and inulin were found to modulate the immune responses in the gut-associated lymphoid tissue (GALT) of chickens like cecal tonsil, enhanced antibody titres of plasma IgM and IgG, cecum IgA levels, mucin mRNA expression and also enhanced intestinal immune functions (Huang ., 2015). Prebiotic treated group (both MOS and FOS) had similar performance to an AGP treated group with better GALT immunity in chickens (Janardhana ., 2009). Prebiotic-mediated immunological changes may in part be due to direct interaction between prebiotics and gut immune cells as well as due to an indirect action of prebiotics preferential colonization of beneficial microbes and microbial products that interact with immune cells (Janardhana ., 2009). In a study by Huang . (2015), dietary inulin supplemented at 5-10 g/kg had better effects on a starter phase (0-21 d) in both feed intake and intestinal IL-6, IgA, CD8, CD4 lymphocytes, and did not have any effect on d 42 broiler chicks.


Fig 1. Prebiotics in immunomodulation (Adapted from Monsan and Paul, 1995)


Advantages of prebiotic supplementation:

  1. Antagonism towards pathogens

  2. Competition with pathogens

  3. Promotion of enzyme reaction

  4. Increase of resistance to colonization

  5. Improve gut health and improve intestinal microbial balance

  6. Improve performance of poultry

  7. Enhance nutrient utilisation (amino acids and proteins)

  8. Improvement of intestinal environment by decrease in intestinal putrefactive substances induced by ingestion of 4g of lactulose (Mizota et al., 2002) showing potential role of prebiotic in controlling environmental pollution.

  9. Decrease production cost


Conclusion

Keeping above all, it can be concluded that use of prebiotics in poultry feed as alternatives to growth promoters is beneficial against enteropathogens which contributes to economic benefits. These preparations are extremely important source in poultry production through improvement of immunity and health status.


Authors

1 Ph.D. Scholar, RAJUVAS, Bikaner, Rajasthan

2 Assistant Professor (AN), RAJUVAS, Bikaner, Rajasthan

3 Ph.D Scholar, ICAR-NDRI, Karnal- 132001, Haryana

4 Ph.D Scholar, ICAR-NDRI, Karnal-132001, Haryana

5 Ph.D Scholar, RAJUVAS, Bikaner, Rajasthan

6 Ph.D Scholar, RAJUVAS, Bikaner, Rajasthan

References

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