MUSCLE-FIBER TYPE AND SIZE, AND MUSCLE CAPILLARY DENSITY IN YOUNG DOUBLE-MUSCLED BLUE BELGIAN CATTLE

Bovine muscle biopsies were analysed for fiber type and capillary dens ity by the acid ATP-ase and amylase-PAS methods respectively. Samples obtained from Belgian blue double muscled (DM) calves were compared fo r their fibre type, size and vascularization with samples from Friesia n (F) calves. The animals were sampled both at 2 and 7 months of age. Changes in histochemical composition occurring with ageing, independen tly of the breed, and differences related to the muscle sampled by com paring biopsies obtained from the longissimus dorsi (LD) and gluteobic eps (GB) muscles in animals of both breed were also investigated. Inde pendently of age and muscle, fibre type I percentage and area were sig nificantly higher in F than in DM muscles. Type IIa area was significa ntly larger in F than in DM, while fibre type IIb percentage and area were higher in DM. The number of capillaries/mm2 was significantly hig her in F than in DM. Fibre type IIa and IIb percentage as well as the diameter of the three fibre types was significantly higher in the olde st animals. Finally, independently of age and breed, fibre type I and IIb percentages were significantly higher in LD but lower in GB. The r esults mainly demonstrated that Belgian blue DM muscles present a high er proportion of IIb fibres and a lower capillary supply than F muscle s.