Effect of sire breed on growth, carcass, and wool characteristics of lambs born to Merino ewes in New Zealand

Sire breed effects were studied in 1080 lambs born over three years to Merino ewes and 6 10 sires each of Merino, Poll Dorset, Border Leicester, Texel, Oxford Down, and Suffolk breeds. Ewes bearing crossbred lambs required more assistance at lambing than those with purebred Merino lambs. Poll Dorset cross lambs grew fastest and purebred Merinos slowest from tailing until they were 12 months old (P < 0.05). While purebred Merinos tended to have less carcass fat throughout the trial, differences between the other crossbreds changed with time. Texel and Poll Dorset cross carcasses generally had larger eye muscle size (P < 0.05) than other sire breeds. Carcasses were "blockier" for crossbreds, particularly Texel and Oxford Down, but weights of individual cuts were similar for all breeds. At 12 months of age, greasy fleece weights were heaviest (P < 0.05) in Border Leicester cross lambs (4.4 kg) and least in Suffolk crosses (3.1 kg). It is concluded that Merino cross lambs can produce 20-kg carcasses by 9 months of age under improved pasture conditions. Local sire breeds were competitive with more recently imported sire breeds for meat production.