Dynamic distribution of gut microbiota in posthatching chicks and its relationship with average daily gain

The colonization and development of gut microbiota are essential for the health and growth of chicks after hatching. However, the colonization and prevalence of gut microbiota have not been well characterized, and knowledge of which microbes and their relationship with average daily gain in chicks is still limited. This study characterized the dynamic succession of microbiota in the intestinal tract of chicks and investigated its relationship with daily weight gain. A total of 121 fecal samples across 7 time points from d 0 to 10 posthatching were collected from 19 chicks randomly selected from 1,950 chicks. Using 16S rRNA gene sequencing examined microbial composition of fecal samples. The observed species index of alpha diversity increased with age, gradually achieving stability at 3 d of age. The microbiota of chicks after hatching was primarily Clostridium_sensu_stricto_1 (34.49%), and its relative abundance diminishes with age. In contrast, Lac-tobacillus had a low relative abundance in the first 2 d after hatching and gradually increased with age. Predicted functional capacities found that the microbiota of early-stage posthatching (d 0 and 1 after hatching) was involved in metabolism, including amino acid metabolism, metabolism of cofactors and vitamins, and nitrogen metabolism. However, at the later stage posthatching (from d 3-10 after hatching), the intestinal microbial function was involved in carbohydrate metabolism, amino acid metabolism, cell growth and death, and methane metabolism. It was identified that 47 operational taxonomic units were associated with average daily gain of chicks, 12 of which were annotated with Lactobacillus and significantly positive associated with average daily gain. In addition, Clos-tridium_sensu_stricto_1 was significantly negatively associated with average daily gain. Taken together, we characterized the dynamic successions of intestinal micro-biota in hatching chicks. The intestinal microbiota of chicks has an impact on the host average daily gain. Our findings should be instrumental in improving local chick