Abstract
Muscle fibers in five different skeletal muscles of the steers were histochemically classified into five types. The type A reacted strongly for myosin ATPase and phosphorylase and moderately to strongly for succinate dehydrogenase (SDH) and NADH-diaphorase. The type B reacted strongly for myosin ATPase and phosphorylase and weakly for SDH and NADH-diaphorase. The type C reacted weakly for myosin ATPase, weakly to moderately for phosphorylase, and strongly for SDH and NADH-diaphorase. The type D reacted very weakly for myosin ATPase and phosphorylase, moderately to strongly for SDH, and strongly for NADH-diaphorase. The type E reacted moderately for myosin ATPase, weakly for phosphorylase, and very strongly for SDH and NADH-diaphorase. The β-hydroxybutyrate dehydrogenase (β-HBD) reaction was negative to very weak in the A fibers, negative in the B fibers, and very weak to moderate in the C fibers; it was moderate in the D fibers and very strong in the E fibers. The D fibers of the M. serratus ventralis were larger than four other types. The M. longissimus thoracis consisted of the A, B, and C fibers. The M. semitendinosus, M. serratus ventralis, and M. supraspinatus contained the A, B, C, and D fibers. The M. masseter consisted only of the E fibers.
