Histochemical Properties of Skeletal Muscles in Different Body Parts of Young Japanese Black Steers

抄録

Histochemical examination was carried out on the 66 skeletal muscles in the different body parts of the young Japanese Black steers (11 months of age). Tissues were taken from the central portion of each muscle, cut into serial frozen sections and stained by reactions for myosin ATPase and NADH dehydrogenase activities. Myofibers were divided into Type I, IIA and IIB. Generally the muscles in the young steers contained Type IIA myofibers at higher frequency as compared with the fattened adult. Some Type IIA myofibers seemed to transform into Type I or Type IIB with age. The muscles with much Type I myofibers which are to play a main role in posture maintaining were very small and occupied the deep position, but Mm. serratus ventrales is fairly large. The large muscles important for beef production contained great proportion of Type II myofibers, which are mobilized to do more active motions such as locomotion. These results suggest that every muscle plays its peculiar function at different body parts after obtaining its own histochemical property.