ABSTRACT Intestinal digestibility can be affected by the interaction between host and gut microbiota, which could influence feed efficiency in poultry. In this study, the performance of 1480 10-week-old Wannan Yellow chickens was recorded for 6 weeks, and the feed conversion ratio (FCR) was calculated. Thirteen 16-week-old chickens (7 in the high and 6 in the low FCR group) were selected for carcass performance, ileum structure, and microbiota composition analysis. The results showed that ileum weight and length were significantly higher (p