Effects of calcium level, acidification by replacing calcium carbonate with calcium formate or by adding formic acid, and phytase on phytate degradation and the microbiome in the digestive tract of broiler chickens. Chicken microbiota Ca effect

The objective of the present study was to evaluate effects of dietary calcium (Ca) source, Ca level, and phytase supplementation on intestinal pH, phytate (InsP6) degradation, prececal (pc) phosphorus (P) and Ca digestibility, and the microbial community in the digestive tract in broiler chickens. Experimental diets were mixed following a 3×2×2 factorial design with 3 Ca sources (CaCO3, CaCO3+formic acid, Ca-formate), 2 Ca concentrations (5 and 8 g/kg DM), and 2 phytase supplementation levels (0 and 1,500 FTU phytase/kg). A total of 1,080 birds were fed the experimental diets from d 16-21/22. At the end of the experiment, digesta from the crop, gizzard, and terminal small intestine wereas sampled. Digesta pH was influenced by all factors under investigation. Influences on digesta pH differed between sections of the digestive tract. 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 down to myo-inositol. Replacing CaCO3 by Ca-formate and the high level of these Ca sources reduced pc InsP6 disappearance. Supplementing phytase to CaCO3+formic acid led to the highest InsP6 disappearance of 52% in the crop and increased myo-inositol concentration in the ileum digesta. The pc P digestibility was lower in diets with the a high Ca level and was reduced with Ca-formate. The microbiota was influenced by all factors. Among Ca sources, Ca-formate was different fromto CaCO3 and CaCO3+formic acid. In terms of predicted functionality of the microbiota, different responses for Ca-formate than for the other Ca sources were determined. InsP6 degradation and the microbiota were similarly influenced by treatments. Whether changes in the microbiota influenced the InsP6 degradation or diets influenced microbiota and InsP6 degradation independent of each other still is to be clarified. The results of the present study show that considering Ca sources is necessary when the effects of Ca level and phytase supplementation on InsP6 degradation and P digestibility are discussed.