Impact Of Added Phytase And Dietary Insp6 On The Structure And The Core Microbiota Of The Digestive Tract Of Broilers

The Myo-inositol (1,2,3,4,5,6) hexakis (dihydrogen phosphate) (InsP6) concentration in the feed varies with the raw material used. Exogenous phytase may be added to the feed at an activity level adjusted to the InsP6 concentration. Our goal was to explore the composition and functionality of the gut microbiome in the context of varying exogenous phytase levels combined with increasing levels of InsP6. Twelve experimental diets were created by combining 3 phytase levels (500, 1500, and 3000 FTU/kg) with 4 feed mixtures (FM) to achieve varying levels of InsP6 (1.4, 1.9, 2.4, and 3.0 g InsP6/kg). InsP6 level was adjusted in each FM by substituting maize starch with a constant ratio of oilseed meals and rice bran. A total of 840 Ross 308 broiler hatchlings were raised at standard conditions. On days 0 (L0) and 14 (L14), litter was sampled from the ground. On day 14, the animals were weighed and evenly distributed into 84 metabolic cages; each of the 12 experimental diets (ED14) was sampled and randomly allocated to 7 cages. The broilers were slaughtered on days 22 and 23, and digesta from the crop, ileum, and ceca were collected. Leftovers from the experimental diets (ED22) were collected from the feeder on the same day. Digesta samples were pooled on a pen basis, and immediately stored at -80°C until further analysis. DNA extraction was done with a commercial kit, and 16S rRNA gene target sequencing was performed. In the crop, the FM2.4 and FM3.0 reduced Lactobacillus and increased Ligilactobacillus, compared to FM1.4, while phytase increased the relative abundance of Ligilactobacillus. In the ileum, Lactobacillus increased with the phytase addition and it was reduced in FM3.0 compared to FM1.4. Streptococcus increased in FM3.0 compared to FM1.4. In the ceca, FM3.0 increased the abundance of Ligilactobacillus, Streptococcus, and Subdoligranulum compared to FM1.4. A core microbiota across all samples was not detected. Lactobacillus crispatus was present at high abundance in the crop (49%), ileum (42%), and ceca (24%). Phytase supplementation and increasing dietary inclusion of oilseed meals and rice bran at the expense of starch aiming at increased InsP6 concentration, significantly affected a-diversity in the ceca. Lactobacillus and Ligilatobacillus were identified as the drivers of colonization in the gut, implying their resilience and dominance in relation to the persistent ASV across the intestine.