Muscle-specific variation in beef quality traits across genetic groups of forage-fed young bulls

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Abstract
Beef quality reflects both intrinsic muscle characteristics and animal-related factors, including genetic background. However, the extent to which muscle-specific quality patterns are consistent across genetic backgrounds remains poorly understood. This study evaluated the multivariate structure of beef quality traits across muscles and genetic backgrounds. Nineteen young bulls from two contrasting genetic backgrounds (Charolais × Salers and Salers) were studied. Four muscles differing in anatomical location and metabolic function (Longissimus thoracis, Semitendinosus, Rectus abdominis and Diaphragm) were analysed for technological, mechanical, compositional and fatty acid-related nutritional traits. Linear mixed-effects models, fixed-effect variance decomposition, muscle hierarchy analyses, Spearman rank correlations and principal component analysis were performed. Muscle type accounted for the largest proportion of explained variation (around 68%) for most technological, compositional and mechanical traits, whereas genetic background made a comparatively smaller contribution. Muscle rankings were broadly consistent across genetic backgrounds for technological, and compositional traits, and showed greater trait-dependent variation for mechanical and nutritional traits. The first two principal components explained 83.7% of the total variation. Dimension 1 separated muscle profiles with greater lightness and mechanical resistance from profiles with higher intramuscular fat and lipid-related variables. Semitendinosus and Diaphragm occupied opposite positions along this axis, whereas Longissimus thoracis and Rectus abdominis displayed intermediate profiles. Within the forage-based production conditions and genetic backgrounds examined, beef quality variation was more strongly associated with muscle type than with genetic background. These findings support muscle-specific evaluation and interpretation of carcass quality traits, while requiring confirmation in larger and more diverse animal populations and production systems.