Impact of ground soybean and starch levels on the quality of meat from feedlot young Nellore bulls

•The inclusion of lipid sources in cattle feed may modify the fatty acid profile of the beef.•The diet containing ground soybean increased polyunsaturated fatty acid.•High-starch diets decreased saturated fatty acids in the meat from young Nellore bulls.•C16 and C18 Δ9-desaturase enzyme activities were greater in the muscle from animals fed without ground soybean.•A lower atherogenicity index was observed in the muscle from animals fed with ground soybean.

Twenty-eight young Nellore bulls (395 ± 32 kg initial body weight) were assigned to a completely randomized design (2 × 2 factorial design with 7 animals per treatment) to evaluate effects on the quality of meat. Diet treatments consisted of high (about 25%) or low (about 16%) starch levels, with or without ground soybean addition. Shear force was decreased in the meat from animals fed a low-starch diet (P = 0.0016). Meat from animals fed a high-starch diet had increased total concentrations of unsaturated (P = 0.0029) and monounsaturated fatty acids (P = 0.0253). Polyunsaturated fatty acid content increased in the meat from animals fed a diet containing soybean (P = 0.0121). High starch diets (> 25%) decreased the concentration of saturated fatty acids and increased the amount of unsaturated fatty acids in the meat from young Nellore bulls.