Comparison of terminal sire breeds for growth and carcass traits in crossbred lambs

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Abstract
Performance records for the progeny of matings of Oxford, Texel, Texel-Oxford, Charollais, Charmoise and Meatlinc rams with crossbred ewes were analysed. The lambs, born from 1980 to 1982, were randomly allocated to three slaughter groups: (1) slaughter at fixed weights of 36 and 38 kg for ewe and castrated lambs; (2) slaughter according to estimated fat cover; (3) slaughter at a fixed age of 4·5 or 5·5 months with half-carcass dissection. The analyses were by least squares and effects were fitted for terminal sire breed, breed of maternal grand sire, year of birth, age of dam at lambing, birth-rearing type and sex of lamb and all two-way interactions. The results followed a well-established pattern where weight for age rankings were constant from birth, through weaning, to slaughter. Progeny of Oxford rams were the heaviest, followed by Texel-Oxford, Meatlinc and Charollais, Texel and Charmoise in that order. Lambs sired by rams of low mature weight reached a fixed weight at a later age than those sired by rams of high mature weight. They also reached a similar degree of fat cover at an earlier age and at lighter weights than the larger breeds. The carcass traits indicated that Texel crosses had a higher lean and lower fat proportion than would be expected from their growth and mature weight.The comparative performance of crossbred lambs from 15 terminal sire breeds was assessed, at the same proportion of carcass subcutaneous fat, by combining the results of three experiments.