Determinants and effects of postileal fermentation in broilers and turkeys part 1: gut microbiota composition and its modulation by feed additives

Abstract

Postileal fermentation in the gastrointestinal tract of poultry takes place as a result of the interaction between two components of the intestinal ecosystem: rapidly changing microbiota and digesta with different physicochemical properties. Short chain fatty acids, the major products of fermentation, act to stabilise microbiota composition and maintain gut health, and constitute an additional source of energy. Due to different mechanisms of action of probiotics, phytobiotics and prebiotics in the intestinal ecosystem, the quantities and proportions of the major products of fermentation are affected by the type of feed additives. Some phytobiotics, including alkaloids, exert antimicrobial effects and reduce short chain fatty acids concentrations in the caecum. Mannan-oligosaccharides, regarded as prebiotics, may prevent the adhesion of pathogenic bacteria (mostly E. coli and Salmonella) to the gut wall. Prebiotic oligosaccharides, in particular fructo-oligosaccharides and inulin, are used by beneficial bacteria of the genera Bifidobacterium and Lactobacillus, thus enhancing the synthesis of short chain fatty acids in the lower gastro intestinal tract of poultry, while low intestinal pH inhibits the growth of pathogenic bacteria.