Effect of grazing in the latter fattening period on the nutrient content and gene expression in steer muscle

摘要

This study investigated the nutrient content in muscle and gene expression for muscle development between indoor concentrate-fed and outdoor grazed steers. Ten Japanese Black steers were randomly selected and divided into two groups: grazing (GR) and concentrate (CT) groups. Crude protein and extractable lipid in muscle tissue were analyzed. The gene expression of myosin heavy chain (MyHC), myostatin, peroxisome proliferator-activated receptor γ2 (PPARγ2), and CCAAT/enhancer binding protein α (C/EBPα) in skeletal muscles was evaluated by real-time PCR. In the semitendinosus (ST) and longissimus lumborum (LL) muscles, extractable lipid content was lower in the GR group than in the CT group. Crude protein content in the LL muscle in the GR group was higher than that in the CT group. MyHC expression in LL muscle in the GR group was greater than that in the CT group. A decrease in the expression of myostatin (a specific negative regulator of skeletal muscle growth) was detected in the GR group compared with the CT group in both muscles. In the ST and LL muscles, PPARγ2 gene expression was lower in the GR group than in the CT group. These results suggest that the increase in protein content and decrease in fat accumulation in LL and/or ST muscles of the grazing group were affected by the expression of myostatin, MyHC, PPARγ2, and C/EBPa genes.