The aim of the present work was to study the relative development of liveweight components, regional composition and tissue composition of shoulder and hindquarter in Australian Merino, Polwarth, Corriedale, Romney Marsh and Texel lamb. The study was carried out at the Centro de Pesquisa de Pecuária dos Campos Sulbrasileiros of EMBRAPA (CPPSUL/EMBRAPA), located in Bagé, state of Rio Grande do Sul, Brazil. Fifty lambs, ten of each breed, were used, born and raised up to weaning (10 weeks) on native pasture. After weaning, they were fed with a concentrate (200g/lamb/day), containing 17% of crude protein and 75% of dry matter basis, which was offered in confinement until one week. After this, they were put onto paddoks and slaughtered at 7.5 months of age. The study on the relative development of liveweight was done by using the equation: Y = a . x b. The genotype had an effect on the relative development of liveweight components, and both regional composition and tissue composition. By increasing the liveweight, there was proportional increase in the hot carcass weight in Australian Merino, Romney Marsh and Texel breeds. In Polwarths and Corriedales, the development of both traits was similar. The liveweight components in all genotypes were non significant with exception of head in Romney Marsh and Texel lambs, which showed a late development, and of spleen in Australian Merino lambs, which showed a late development. Related to cold carcass, the neck region had an early development in Corriedale and Romney Marsh lambs, while the rack was late in Romney Marsh lambs. Other cuts showed a similar development in all genotypes. Based on the results of this work, it can be stated that the slaughtery weight of lambs is influenced by genotype.
allometric growth; body parts; carcass; lambs; live weight components; tissue composition
