Intestinal segment-specific microbiota profiles correlate with body weight divergence in Ningdu yellow chickens.

The Ningdu yellow chicken, a premium indigenous breed, has its growth performance as a major focus of its breeding. While the gut microbiota is recognized as a key regulator of host metabolism and health, its specific role in driving body weight (BW) variation in this breed remains unclear. To address this, we characterized the microbial communities in the jejunum, ileum, and cecum of chickens across a BW spectrum using 16S rRNA sequencing, aiming to elucidate how microbiota composition and structure correlate with, and potentially collectively influence on BW. Our findings revealed that the effect of BW on microbial diversity depends heavily on the intestinal segment. Notably, the cecum exhibited significantly higher alpha diversity than the small intestinal segments across all BW groups, establishing the intestinal segment itself as the primary determinant of community structure. We identified several BW-associated bacterial species. For instance, Lactobacillus saerimneri was positively correlated with BW in the jejunum, whereas most differentially abundant species in the ileum exhibited a negative correlation trend. Of particular interest, Mordavella sp. Marseille-P3756 and Blautia glucerasea demonstrated the strongest positive correlation with BW in the cecum, highlighting them as priority candidates for future functional studies. Collectively, this work provides novel insights into the segment-specific interplay between gut microbiota and BW in Ningdu yellow chickens, thereby establishing a scientific foundation for developing targeted microbial interventions, such as probiotic formulations, to enhance breeding efficiency.