The influence of breed, castration and age on muscle fibre type and diameter in friesland and Afrikaner cattle

Abstract

SUMMARY.. Bulls and steers from Afrikaner and l'riesland cattle fed od lib. were slaughtered at different ages from birth to 24 months inclusive. Sampfes were taken fronr the M. semimembranosus and M. semitendinosus (dark and light) and histochemically treated with succinic dehydrogenase f'or red and white muscle l'ibre identification. Muscle libre diameter was also determined. No pirouping into any particular pattern of the nruscle tibrc types could be observed. A gradual transition from red to white muscle fibre types occurs with age. The I':riesland has a larger percentage white nluscle fibrcs and a lower percentage red muscle fibres than the Afrikaner for the muscles concerned. Bulls havc a larger perccntage red muscle t-ibres and a lower percentage white nruscle tlbres than the ste€rs The increase in mux'fe fibre dianreler t'ollows a characteristic pattern for the particular musclcs. The M. semimembranosus and the M. semitendinosus (dark area) show an incrcase in diameter up to l2 m<lnths before tapering off while the M. semitendinosus (light area) shows an increase up to 20 months before levelling off. White rnuscle fibre diameter is larger than red muscle fibre diamcter at all ages Tire Afrikaner bulls have a smaller mean fibre drarneter than l;riesland bulls. The bulls, however, have a larger mean muscle fibre diamcter than thc steers notwithstanding the lowcl percentage of white muscle fibres. Thc possible relationship between the type of muscle rnetabolism and meat q uality characteristics is dix'usscd.