Impact of added phytase and different dietary InsP6 levels on the structure and core microbiota of the digestive tract in broiler chickens

The main objective of this research was to investigate the composition and shifts of the gut microbiota of broiler chickens in response to varying exogenous phytase combined with increasing levels of myo -inositol (1,2,3,4,5,6) hexakis (dihydrogen phosphate) (InsP 6 ) in the feed. The InsP 6 level was adjusted with the addition of oilseed meals (OSM) at the expense of maize starch. A secondary objective was to assess the existence of a core microbiota across the feed, litter and gastrointestinal tract (GIT). A total of 840 Ross 308 broiler chickens were raised in 84 elevated pens in groups of 10. The treatments consisted of four feed mixtures (FM) designed to achieve 1.4 (FM1.4), 1.9 (FM1.9), 2.4 (FM2.4), and, 3.0 (FM3.0) g InsP6-P/kg, each combined with 500, 1500 or 3000 FTU phytase/kg. In the crop and the ileum, Lactobacillus relative abundance decreased when OSM and phytase increased (p < 0.05), while FM2.4 and FM3.0 were associated with increased Ligilactobacillus abundance across the GIT (p < 0.05). No interaction effects were found across the studied sections (p = 0.22). Four amplicon sequence variants (ASV), identified within the genera Lactobacillus, Ligilactobacillus, and Limosilactobacillus were consistently found across the intestine sections. These four ASVs represented 58.9 % of the relative abundance in the crop, 72.9 % in the ileum and 29.7 % in the ceca. The results demonstrated that higher levels of OSM in the feed and exogenous phytase significantly affected these bacterial populations, decreasing Lactobacillus while increasing Ligilactobacillus , indicating independent effects of FM and phytase supplementation. • Four amplicon sequence variants were consistently detected across the gastrointestinal tract. • Oilseed meal supplementation decreased Lactobacillus and increased Ligilactobacillus. • Lactobacillus and Ligilactobacillus showed divergent responses related to sucrose levels. • Phytase supplementation reduced Lactobacillus and increased Ligilactobacillus abundance. • Ligilactobacillus may produce phosphatases under a broader range of conditions.