Food and Medicine Homology Substances as Potential Modulators of the Gut–Muscle Axis in Animal Meat Quality: A Review

Food and medicine homology (FMH) substances are increasingly utilized as nutritional and medicinal resources in sustainable livestock production. Their active ingredients include polysaccharides, flavonoids, and terpenes, which may positively affect livestock meat quality by maintaining gut microbiota homeostasis, enhancing intestinal barrier function, and facilitating nutrient absorption, as well as regulating key signaling pathways such as mechanistic target of rapamycin (mTOR), AMP-activated protein kinase (AMPK), and nuclear factor-κB (NF-κB). Notably, the meat quality improvement can also be indirectly achieved via the gut–muscle axis. Gut microbiota metabolites, including short-chain fatty acids (SCFAs), bile acids (BAs), and amino acid derivatives, modulate microbial homeostasis, intestinal barrier function, and nutrient absorption through the gut microbiota–metabolite axis, gut–immune axis, and nutrient absorption–signaling axis. These processes remotely regulate skeletal muscle metabolism, inflammation, and fiber type transformation, ultimately influencing meat tenderness, flavor, juiciness, and nutritional value. Despite their potential to reduce reliance on antibiotic growth promoters and enhance meat quality, multiple challenges persist, including complex component profiles, elusive mechanisms, undefined dose–effect relationships, inadequate standardization, insufficient safety evaluation and scarce direct trials on livestock meat quality endpoints. This review summarizes FMH substances that modulate the gut–muscle axis in meat quality regulation across different animal species and outlines their application prospects, aiming to facilitate antibiotic-free agriculture, the development of green functional feeds, and sustainable animal husbandry.