Variations in Intramuscular Fat Content and Profile in Angus × Nellore Steers Under Different Feeding Strategies Contribute to Color and Tenderness Development in Longissimus thoracis

Muscle from cattle reared under different finishing regimes (grain vs. forage) and with different growth rates may have divergent metabolic signatures that are reflective of their inherent differences in biochemical processes, which may impact their subsequent transformation into high-quality beef. Differences in muscle lipid profiles were characterized in Angus × Nellore crossbred steers, using multiple reaction monitoring profiling, to identify potential metabolic signatures correlated to beef color and tenderness in the longissimus thoracis muscle of cattle fed in either a feedlot-or pasture-based system programmed to achieve either a high or low growth rate. A total of 440 lipids were significant, which were related mainly to triglycerides and phosphatidylcholine lipids. Distinct clusters between feeding strategies for the lipid dataset were revealed, which affected glycerolipid metabolism (P = 0.004), phospholipid metabolism (P = 0.009), sphingolipid metabolism (P = 0.050), and mitochondrial beta-oxidation of long-chain saturated fatty acid (P = 0.073) pathways. Lipid content and profile differed with feeding strategies, which were related to L*, a*, and tenderness. These findings provide a comprehensive and in-depth understanding of lipidomic profiling of beef cattle finished under different feeding strategies and provide a basis for the relationship between lipid content and profiles and beef quality development.