Carcass characteristics of heavyweight crossbred lambs. I. Growth and carcass measurements

Abstract

An experiment was conducted at Temora Agricultural Research Station to assess the potential for producing heavyweight lamb carcasses from breeds currently used in the prime lamb industry. Growth to slaughter, dressing percentage and carcass measurements of lambs from six breed crosses were compared over a range of carcass weights. The lambs were the progeny of Dorset Horn and Border Leicester rams joined to Merino, Corriedale and Border Leicester x Merino first-cross ewes. Within each breed combination, lambs were allocated to be slaughtered at 34, 44 or 54 kg liveweight.

Lambs sired by Dorset Horn rams were slightly larger at birth and weaning, and reached their slaughter weights at a younger age, than lambs sired by Border Leicester rams. Lambs from Border Leicester x Merino ewes grew 10% faster than lambs from Corriedale ewes. The progeny of Merino ewes were always slowest-growing, and this was more marked at higher weights. Carcasses from the slower-growing genotypes tended to be larger in skeletal size and had a lower dressing percentage than carcasses from faster-growing genotypes, when adjusted to the same carcass weight. Fat depth at the 12th-13th rib increased, on average, by 20% for each 10% increase in carcass weight, over the range of carcass weights examined. The rate of increase in carcass fatness was significantly lower in lambs sired by Dorset Horn rams and lambs from Merino ewes, compared with lambs of the other breeds.