Host genetic and gut microbiota interactions regulating intramuscular fat deposition in livestock: mechanistic insights and implications for meat quality.

Intramuscular fat (IMF) is a major determinant of meat quality, influencing tenderness, juiciness, flavor, oxidative stability, and nutritional value in livestock products. Increasing evidence indicates that IMF deposition is regulated by complex interactions between host genetics and gut microbial metabolism. This review summarizes current advances in the molecular and metabolic mechanisms linking host genetics and gut microbiota to IMF accumulation and meat quality traits. At the host level, IMF deposition is regulated by coordinated adipogenic networks involving PPARγ-C/EBPα signaling, lipogenic regulators, nutrient-sensitive pathways, and epigenetic modifications that control adipocyte differentiation and lipid storage. In parallel, the gut microbiota acts as an important metabolic regulator by producing bioactive metabolites, including short-chain fatty acids and secondary bile acids, which influence adipogenesis, inflammation, nutrient partitioning, and metabolic flexibility. Emerging evidence further demonstrates that microbial metabolites can modulate host transcriptional and epigenetic programs, thereby linking microbial activity with tissue-specific lipid metabolism. Integrative multi-omics approaches are increasingly revealing the mechanistic basis of host-microbiome interactions underlying variation in carcass composition and meat quality across livestock species. This review further highlights the translational potential of precision nutrition, microbiome modulation, and microbiome-informed breeding strategies for sustainable meat production.