3.2. Muscle fiber and adipocyte characteristics
The postnatal growth from 6 to 16 months of age of the semitendinosus muscle in cattle was character- ized in total by a 2.6-fold (CH) and a 2-fold (H) increase in muscle fiber cross section area (Table 2) on average for all three fiber types (IIB, IIA, I). At 6 months of age, for the mean of all fiber types, as well as in the type IIB and type I, no differences were found between CH and H bulls. Only in type IIA did the CH bulls show a higher cross sectional area. From the 8th month of age onwards the mean of the muscle fiber cross section area was higher than at the 6th month of age in both breeds and at the age of 16 month higher in CH bulls than in H bulls. Focusing on each of the single fiber type, differences between the two metabolic types of cattle could be observed at 16 months of age and in type IIB also at 13 month of age. The fiber type frequency (Table 3) in the semite- ndinosus muscle was unaffected by breed and age. Small, age-related differences were found only in type IIB fibers of CH bulls.