Performance of sheep on New Zealand hill country

Abstract

The body weights and carcass composition of wether lambs and hoggets of different breeds and crosses run on steep New Zealand hill country and slaughtered at one of three ages (5-6 mth, 10 mth, 15 mth), were measured. The breeds and crosses examined in the trial were Merino x Romney, Romney, Drysdale x Romney, Drysdale, Cheviot, Coopworth, Perendale, and Poll Dorset x Romney. Published results for Merinos and Corriedales from a previous year of the trial were incorporated into overall breed growth rankings. When comparing the mean dressed carcass weights of the superior breeds with those of the Romney for the years that these other breeds were present for comparison, the Cheviot wethers averaged + 3.3 kg, the Coopworth + 3.3 kg, the Perendale + 3.9 kg, and the Dorset x Romney +4.8 kg heavier. Most lambs of these breeds could have been drafted for slaughter off the hills at acceptable carcass weights and grades before their first winter, whereas animals of the remaining breeds and crosses were suitable only for sale as store lambs. Drysdale and Drysdale x Romney lambs grew slightly faster and produced slightly longer-legged carcasses than Romneys. The Perendale grew at least as fast as the Coopworth on these hills, whereas in some previous lowland experiments Coopworth-type lambs grew faster than Perendale-type (Cheviot x Romney) lambs. Breed means for these hill country carcasses showed they were leaner than normal export lamb carcasses. A feature of the carcass composition results was evidence suggesting that in most instances carcass weight gain between 10 and 15 months was lower in fat content than was carcass weight gain between 5-6 months and 10 months. Breed differences were found in measures of carcass shape and composition but although in most instances these were highly significant within birth years, between-year differences suggest the presence of breed x year interactions for these traits.

Keywords:

• hill country
• breeds
• animal growth
• carcass composition
• animal organs
• lambs
• sheep
• wethers
• livestock assessment
• animal quality
• meat production
• fat development
• growth rates
• weight gain
• carcass yield
• carcass quality