摘要Heterosis has been widely utilized in agricultural production.Despite over a century of extensive research,the underlying mechanisms of heterosis remain elusive.Most hypotheses and research have focused on the genetic basis of heterosis.However,the potential role of gut microbiota in heterosis has been largely ignored.Here,we carefully design a crossbreeding experiment with two distinct broiler breeds and conduct 16S rRNA amplicon and transcriptome sequencing to investigate the synergistic role of gut microbiota and host genes in driving heterosis.We find that the breast muscle weight of hybrids exhibits a high heterosis,6.28％higher than the mid-parent value.A notable difference is observed in the composition and potential function of cecal microbiota between hybrids and their parents.Over 90％of differentially colonized microbiota and differentially expressed genes exhibit nonadditive patterns.Integrative analyses uncover associations between nonadditive genes and nonadditive microbiota,including a connection between the expression of cellular signaling pathways and metabolism-related genes and the abundance of Odor-ibacter,Oscillibacter,and Alistipes in hybrids.Moreover,higher abundances of these microbiota are related to better meat yield.In summary,these findings highlight the importance of gut microbiota in heterosis,serving as crucial factors that modulate heterosis expression in chickens.