Abstract
BackgroundDiet acidification, dietary calcium (Ca) level, and phytase supplementation are known influences on the microbial community in the digestive tract and on phosphorus (P) utilization of broiler chickens. Effects of dietary factors and microbiota on P utilization may be linked because microorganisms produce enzymes that release P from phytate (InsP6), the main source of P in plant feedstuffs. This study aimed to detect linkages between microbiota and InsP6 degradation by acidifying diets (i.e., replacing Ca carbonate (CaCO3) by Ca formate or adding formic acid to CaCO3-containing diets), varying Ca levels, and supplementing phytase in a three-factorial design. We investigated i) the microbial community and pH in the digestive tract, ii) prececal (pc) P and Ca digestibility, and iii) InsP6 degradation.ResultsAll factors under investigation influenced digesta pH and the microbiota composition. Predicted functionality and relative abundance of microorganisms indicated that diets influenced the potential contribution of the microbiota on InsP degradation. Values of InsP6 degradation and relative abundance of the strains Lactobacillus johnsonii and Lactobacillus reuteri were correlated. Phytase supplementation increased pc InsP6 disappearance, with differences between Ca levels, and influenced concentrations of lower inositol phosphate isomers in the digestive tract. Formic acid supplementation increased pc InsP6 degradation to myo-inositol. Replacing CaCO3 by Ca-formate and the high level of these Ca sources reduced pc InsP6 disappearance, except when the combination of CaCO3 + formic acid was used. Supplementing phytase to CaCO3 + formic acid led to the highest InsP6 disappearance (52%) in the crop and increased myo-inositol concentration in the ileum digesta. Supplementing phytase leveled the effect of high Ca content on pc InsP6 disappearance.ConclusionsThe results point towards a contribution of changing microbial community on InsP6 degradation in the crop and up to the terminal ileum. This is indicated by relationships between InsP6 degradation and relative abundance of phosphatase-producing strains. Functional predictions supported influences of microbiota on InsP6 degradation. The extent of such effects remains to be clarified. InsP6 degradation may also be influenced by variation of pH caused by dietary concentration and solubility of the Ca in the feed.
Highlights
Diet acidification, dietary calcium (Ca) level, and phytase supplementation are known influences on the microbial community in the digestive tract and on phosphorus (P) utilization of broiler chickens
When diets are fed with the supplementation of mineral P and calcium (Ca), but without supplemented phytase, prececal myo-inositol 1 (InsP6) degradation is reduced in broiler chickens [1]
Growth performance The average daily gain (ADG) and average daily feed intake (ADFI) during the experimental period were lower compared to other treatments when the Ca level was high and no phytase was supplemented (P < 0.001; Fig. 1, Table S1)
Summary
Dietary calcium (Ca) level, and phytase supplementation are known influences on the microbial community in the digestive tract and on phosphorus (P) utilization of broiler chickens. Effects of dietary factors and microbiota on P utilization may be linked because microorganisms produce enzymes that release P from phytate (InsP6), the main source of P in plant feedstuffs. High utilization of phosphorus (P) provided by plant feedstuffs is advantageous because less or no mineral P is needed to fulfill the P requirement of animals. When diets are fed with the supplementation of mineral P and calcium (Ca), but without supplemented phytase, prececal (pc) InsP6 degradation is reduced in broiler chickens [1]. The reduced degradation of InsP6 upon Ca supplementation is usually explained, among other reasons, by the formation of Ca-InsP6 complexes in the digestive tract at high Ca concentrations [2, 3]
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