Carcass composition and growth patterns for muscle, fat and bone were compared among 277 young male progeny of eight sire breeds, serially slaughtered at 300 kg live weight, 12 months and 15 months of age. The sire breeds were Simmental (SIM), Charolais (CHA), Danish Red and White (DRK), Romagnola (ROM), Chianina (CHI), Hereford (HER), Blonde d'Aquitaine (BDA) and Limousin (LIM). Tissue growth patterns among breeds were examined by regression estimates from the allometric growth equation (Y = ax h ) and compositional differences were estimated from the intercepts. No significant sire breed differences were found in the regression of muscle, fat or bone on various size dimensions. In regressions involving fat, however, the fattest (HER) had higher regressions and the leanest (BDA) fattened more slowly relative to muscle and bone growth. Breeds differed significantly in amount of muscle, fat and bone when compared at standard weights. Sire breed ranking for muscle at common bone weights was LIM, BDA, CHA, SIM, HER, ROM, DRK and CHI, while at common carcass weights the ranking was BDA, CHA, LIM, CHI, ROM, SIM, DRK and HER, reflecting differences in fatness. Minor changes in ranking occurred when comparisons were made at a common live weight reflecting differences in dressing percentage. For fat at standard muscle, carcass or live weight the breeds ranked HER, LIM, DRK, SIM, ROM, CHA, CHI and BDA.
