Our study investigated how different levels of antioxidants and contrasting proportions of native legumes in the diet affect lamb meat quality. Twenty-four male Texel lambs were randomly assigned to three groups: two groups on a natural pasture in southern Brazil (Pampa Biome), each at a different proportion of legumes: Low-legume (LL, 4.37%) and High-legume (HL, 14.01%); the other group was stall-fed (Control) to achieve the same growth rates as the grazing groups. Cold carcass yield from the Control lambs was higher than HL. The meat from pasture-fed animals had a higher deposition of muscle α-tocopherol and lower lipid oxidation (TBARS values) after 9 days of storage. LL lambs had higher subcutaneous fat thickness, which promoted better sensory quality of the meat, as assessed by a trained panel. Pasture-based diets enhanced odd- and branched-chain fatty acids (OBCFAs), trans vaccenic acid, and total conjugated linoleic acids (CLAs), while decreasing elaidic acid. Despite the lower ∆9-desaturase activity, the higher proportion of Desmodium incanum (condensed tannin-rich native legume) in the HL diet did not impact meat nutritional quality. Finishing lambs on the Pampa Biome grasslands is an option for improving the oxidative stability and beneficial fatty acid content of lamb meat, which improves product quality and human consumer health.
