Abstract: The aim of this study was to investigate the effect of dietary linseed supplementation on the histological profile of Longissimus dorsi muscle (LD) and meat quality of Sunit sheep. Methods: Totally 20 three-month-old sheep weighing (16.94 ± 1.29) kg with good body condition were randomly divided into control and linseed groups. The linseed group was fed the control diet with 8% replacement of concentrate by linseeds and the experiment lasted for 3 months. The results indicated that the diameter of muscle fibers and the cross-sectional areas of type I and IIB muscle fibers in the linseed group were significantly lower than those in the control group (P < 0.01), whereas the percentage number and area of various muscle fiber types were not statistically significant between both groups (P > 0.05). The linseed group demonstrated a significant increase in the relative expression of MyHCI and MyHCIIx genes (P < 0.01) and an increase in the relative expression of MyHCIIa and MyHCIIb genes (P > 0.05). Skeletal muscle from the linseed group had a statistically significant higher activity of succinate dehydrogenase (SDH) and lower activity of lactate dehydrogenase (LDH) (P < 0.01). Compared with the control group, a significant increase in pH0 (P < 0.05) and a decrease in L* value, pH24 and shearing force (P < 0.01) were observed for The linseed group. There was no significant difference in other meat quality indicators between both groups. Conclusion: The dietary linseed supplementation has a positive effect on improving the color and tenderness of meat by promote the conversion of muscle fiber from glycolytic to oxidized, decreasing the diameter and cross-sectional areas of muscle fiber.

Key words: Sunit sheep, linseed, muscle fiber characteristics, enzyme activity, meat quality