Betaine improves lamb meat quality with oxidative muscle fiber remodeling and enhanced amino acid-derived taste potential.

Improving meat tenderness and flavor potential without relying on excessive fat deposition is a major challenge. This study investigated the effects of dietary rumen-protected betaine (RPB) on lamb meat quality in Hu-sheep. Twenty lambs were fed basal diets with or without RPB (8 g/day) during the 56-day formal trial. RPB improved several meat quality traits, including tenderness, water-holding capacity, and redness, despite reducing intramuscular fat. Notably, RPB enriched total and umami-related amino acids (Glu, Asp), suggesting enhanced amino acid-derived taste potential. RPB supplementation was accompanied by enhanced antioxidant capacity and upregulated oxidative phosphorylation and ribosome biogenesis pathways. This coordinated molecular reprogramming was associated with remodeling toward a more oxidative muscle fiber phenotype, characterized by reduced fiber cross-sectional area. In vitro assays showed that betaine promoted myogenic differentiation toward an oxidative lineage. Collectively, by coupling metabolic and structural remodeling, RPB provides a promising nutritional strategy for high-quality mutton production.