| Summary: | ABSTRACT: The poultry industry is interested in alternatives to antibiotics to improve production performance and reduce the incidence of enteric diseases. For more than a decade, yeast and yeast fermentation products have been used in the feed industry to improve the growth and feed efficiency of livestock. The yeast cell wall is comprised of numerous polysaccharides: mannans, chitin, β-1,3-glucans, and 1,6-glucans. These are the major bioactive molecules that can impart health benefits to the host. Yeast and yeast cell wall products modulate the host immune response, reduce the load of pathogens, and ameliorate the pathologic effects of enteric infections in poultry. The principal mechanisms of action of yeast probiotics and prebiotics are competitive exclusion and antagonism, immunomodulation, effect on digestive enzymes, and direct nutritional benefits. However, only a few species of yeast, such as Saccharomyces have been thoroughly studied for their probiotic potential. Novel probiotic yeast species, such as whole Pichia guilliermondii (Citrsitim) cells, have recently been shown to have probiotic and prebiotic properties and demand further investigation. A thorough understanding of the poultry gut mycobiota is required to formulate tailor-made probiotics and prebiotics for avian enteric diseases.
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