Guanidinoacetic acid enhances Tibetan sheep–meat quality through the gut–muscle axis: insights from metabolome–microbiome integration

This study evaluated whether dietary guanidinoacetic acid (GAA) was associated with meat quality, jejunal microbiota and muscle metabolomic profiles in Tibetan sheep. A total of 120 healthy, 2-month-old, weaned male Tibetan sheep (17.33 ± 0.21 kg) were allocated to four groups: CON, basal diet (control group); LG, basal diet supplemented with 0.08% GAA; MG, basal diet supplemented with 0.10% GAA; HG, basal diet supplemented with 0.12% GAA. The feeding trial lasted 90 days after a 10-day adaptation. Compared with CON, 0.12% GAA was associated with higher relative abundances of selected jejunal taxa ( Eubacterium_nodatum_group , Family_XIII_AD3011_group and Bacillus ) and increased acetate and propionate concentrations. Untargeted metabolomics identified significantly altered muscle metabolites associated with glycerophospholipid metabolism, including PC 37:5, PC 38:4 and LPA 14:0. The HG group also showed higher glutathione peroxidase activity and total antioxidant capacity, a higher a* value and lower shear force. Correlation analyses indicated associations among jejunal microbiota, muscle metabolites and meat-quality traits. These findings provide further evidence supporting the potential use of dietary GAA as a feed additive for improving selected meat-quality traits in Tibetan sheep.