**Acknowledgements**

*Prebiotics and Probiotics - Potential Benefits in Nutrition and Health*

quently modulate host immunity beneficially [45, 101].

by preventing IL-1β-associated macrophage cell death [102].

In a more recent study, GOS prebiotic was in ovo administered to evaluate the modulation of chicken intestinal microflora and demonstrate the molecular responses of the host animal. The study was performed on meat-type chickens, with 3.5 mg GOS delivered by in ovo injection on day 12 of egg incubation, and the analysis of microbial communities and mucosal gene expression was performed at day 42 post-hatching. Results showed that GOS increased the relative abundance of *Bifidobacterium* in the cecum. GOS also upregulated cytokine and barrier function genes in the jejunum and cecum, host defense peptides in the cecum, and free fatty acid receptors in the jejunum, ileum, and cecum, as shown in **Figure 8**, so that it has been demonstrated that GOS prebiotics have a bifidogenic effect in adult chickens, modulating gene expression related to intestinal immune responses and gut barrier

Due to the great concern about AMR, it is imperative to avoid the use of antibiotics as growth promoters and look for effective alternatives that can help poultry production to improve the welfare of the poultry birds, performance, and production costs. As a result of all the studies that have been carried out, we can conclude that dietary addition of prebiotics has a positive effect on poultry production, highlighting the improvement of intestinal health, immune system, control of pathogens, and performance parameters, which are achieved through a series of interrelated mechanisms and interactions involving interactions between the organisms of the intestinal microbiota and the microbiota with the host animal. Nevertheless, effectiveness of prebiotics will depend on many factors, like the type of supplement, doses, composition of the basal diet, animal characteristics, and environmental condition, showing variable effects on poultry species, so that it is necessary to determine conditions under which prebiotics are effective

expressed on the surface of epithelial cells, macrophages, mast cells, and dendritic cells, including toll-like receptors and NOD-like receptors, and once recognized are activated, producing cytokines for the regulation of further innate immune responses [45]. Although little data show direct effects of prebiotics on immune function, some studies have indicated that prebiotics have an improved response to salmonella vaccine, which could be because prebiotics can act as nonpathogenic antigens themselves, being recognized by receptors of immune cells, which conse-

Immunomodulatory effect of prebiotics has been evaluated in vitro and in vivo. For instance, in an in vitro study, the influence of a FOS-inulin prebiotic at 200 μg/ mL on the ability of the chicken macrophage HD11 cell line to phagocytose and kill *Salmonella enteritidis* was tested. The influence on their ability to express selected inflammatory cytokines and chemokines, such as for IL-1β, lipopolysaccharideinduced TNF factor (LITAF), C-C motif chemokine ligand 4 (CCL4) and inducible nitric oxide synthase (iNOS), and nitric oxide production, was also evaluated. Results showed that phagocytosis of SE by macrophages was not affected with the FOS-inulin treatment, but there was a significant reduction of viable intracellular SE in macrophages treated with the prebiotic. On the other hand, prebiotic treatment did not influence the nitric oxide production, thus suggesting that the FOSinulin-mediated bacterial clearance was not mediated by this compound. Similarly, prebiotic treatment has no influence on expression of LITAF, CCL4, nor iNOS; however, IL-1β expression was significantly lower in macrophages treated with FOS-inulin, suggesting that this prebiotic can modulate the innate immune system

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function [32].

**4. Conclusion**

This research was supported by the Arkansas Bioscience Institute under the project Development of an avian model for evaluation early enteric microbial colonization on the gastrointestinal tract and immune function. The authors thank the CONACyT for the doctoral grant number 270730.
