Identification of key gut microbiota and microbial <scp>QTL</scp> in contributing to the significant differences in body weight between two Chinese local chicken breeds

Previous studies have identified genetic loci that are associated with both feed conversion efficiency and gut microbiota in chickens, suggesting that interactions between the host genome and gut microbiota may influence chicken growth. However, the number of microbial QTL and gut microbiota associated with chicken body weight remains largely unknown. To further explore the impact of host-gut microbiota interactions on chicken body weight and to identify gut microbiota associated with chicken body weight, this study strictly controlled environmental interference and obtained phenotypic, genotypic, and gut microbiota composition data from 100 Langshan and Tibetan chickens (with significant differences in body weight) raised under identical standardized housing conditions. Through genome-wide association studies of chicken body weight, microbiome genome-wide association studies, and Mendelian randomization analysis, we have identified 145 microbial QTL as instrumental variables and screened out seven genera that have a significant causal relationship with chicken body weight, including the genera Blautia and Faecalibacterium. This study identified potential molecular and microbial markers associated with chicken body weight, offering a valuable theoretical framework for enhancing economic efficiency in poultry production.