Influence of different feeding systems on the growth performance and muscle development of Japanese Black steers.

This study investigated the growth performance and gene expression for muscle development between grass hay-fed (GH) and concentrate-fed (CT) steers. Daily gain and energy intake during the fattening period of the GH group were lower than those of the CT group. Analysis of C/EBPα, PPARγ2, myosin heavy chain (MHC), and myostatin gene expressions was performed by real-time PCR. Expressions of C/EBPα and myostatin in semitendinosus and longissimus lumborum (LL) muscles were higher in the CT group than in the GH group at the end of fattening. In LL muscle, MHC expression at the end of fattening was greater in the GH group than in the CT group. These results suggest that regulation of adipogenesis and myogenesis by the expression of genes involved in muscle development might have occurred in the skeletal muscle of the GH group by the feeding of grass hay and/or because of the low energy intakes.