Effect of L-Carnitine on Muscle Quality and Antioxidant Capacity of Hybrid Sheep at an Early Stage

L-carnitine supplementation enhances fatty acid oxidation and antioxidant defense mechanisms in livestock. Twenty-four wether lambs were randomly assigned to one of three dietary treatments: a control (basal diet), a low-L-carnitine diet (0.01%), or a high-L-carnitine diet (0.05%). After a 15-day adaptation period, all lambs underwent a 45-day experimental phase to assess the impact of L-carnitine supplementation on performance, carcass, muscle, and antioxidant capacity. Although growth performance did not show significant differences (p > 0.05), muscle pH increased in the L-carnitine group (p < 0.05), while drip loss decreased in both the low- and high-dose groups (p < 0.05). The a* value of the Longissimus dorsi muscle significantly increased (p < 0.01), enhancing meat color saturation (p < 0.05), with a reduction in the hue angle observed in the high-dose group (p < 0.01). L-carnitine supplementation led to an elevated myoglobin content and a higher proportion of oxymyoglobin, driven by a significant increase in MRA activity (p < 0.01). The concentration of L-carnitine was positively correlated with the a* value, which in turn was associated with higher total myoglobin content and a greater proportion of oxymyoglobin. In terms of antioxidant capacity, the L-carnitine group exhibited a significant increase in superoxide dismutase content. Moreover, there was upregulation of TFR1 and CAT expression at the mRNA level, while HEPH showed downregulation (p < 0.01). Significant increases were observed in both content and mRNA expression of LDHB and NADHBR5 (p < 0.01). The addition of 0.05% L-carnitine to the diet significantly enhanced muscle color stability in hybrid sheep. This improvement was primarily driven by a significant increase in MRA activity in the high-dose group, which facilitated the conversion of metmyoglobin to oxymyoglobin, thereby significantly boosting meat quality prospects for the sheep industry.