Integrative Evaluation of Muscle Fatty Acid Composition and Oxidative Status in Morkaraman Lambs Supplemented with Protected Fat

Background/Objectives: Protected fat supplementation can modify the fatty acid composition of ruminant tissues; however, how these changes relate to systemic and hepatic oxidative responses remains poorly understood. This study evaluated the effects of different levels of protected fat supplementation on serum and liver oxidative biomarkers and investigated their relationships with muscle fatty acid composition in Morkaraman lambs. Methods: Forty-five male lambs were assigned to three dietary groups: control (CON), 2% protected fat (PF2), and 4% protected fat (PF4). At slaughter, eight lambs per group were selected for biochemical and muscle fatty acid analyses. Results: Exploratory between-group comparisons indicated differences in serum glutathione peroxidase (GPx) activity (p = 0.009), with lower activity in PF2 than in the other groups and a significant quadratic pattern (p = 0.002). In the liver, exploratory between-group comparisons indicated differences in catalase (CAT) activity (p = 0.013), while quadratic patterns were observed for CAT and GPx and a linear pattern for arylesterase (ARE). Exploratory comparisons also showed lower saturated fatty acids (SFA) and higher monounsaturated fatty acids (MUFA), total n-3 fatty acids, and conjugated linoleic acid (CLA) in the protected-fat groups, together with more favorable n-6/n-3 ratios and atherogenic and thrombogenic indices. After treatment adjustment and false discovery rate correction, no serum-lipid associations remained significant, whereas several associations involving liver biomarkers were retained. Liver paraoxonase (PON) was positively associated with the Δ9-desaturase C14 index and showed significant associations with several individual fatty acids. Exploratory multivariate and network analyses further indicated distinct but related lipid and oxidative metabolic patterns, with liver PON showing the highest connectivity. Conclusions: These exploratory findings suggest tissue- and dose-related patterns in oxidative responses and indicate that hepatic oxidative metabolism, particularly the PON/ARE system, is associated with muscle lipid composition. However, because each dietary treatment was represented by a single group-fed pen, treatment and pen effects could not be separated. Therefore, the between-group findings should be interpreted cautiously. These relationships are correlational and do not establish causality.