Once-breds have less lean, more fat
ONCE-BRED Continental heifers have a much lower killing out % than unbred animals of the same carcass weight, researcher Desmond Patterson told the conference.
Research at the Agricultural Research Institute of Northern Ireland, Co Down and Greenmount College, Co Antrim shows that at equal rates of carcass gain, breeding resulted in a significant reduction in carcass lean content and increased fatness. Dr Patterson said that results provided bad news for advocates of once-bred heifers.
The trial involved 81 Continental maiden heifers – mainly Blonde dAquitaine and Charolais – fed individually on grass silage and concentrates, with feed levels manipulated to ensure equal liveweight gain in bred and unbred animals. Heifers were slaughtered at similar carcass weights and ages. In the study, finished unbred heifers of 620kg liveweight had a carcass weight of 368kg and a killing out % of 59.4%. Once bred heifers weighed 651kg liveweight while their carcasses weighed 363kg, giving a killing out at 55.7%.
"Breeding had a consistently negative effect on killing out yield. Although carcass conformation was not affected, both eye muscle area and the proportion of high priced joints in the side were significantly reduced by breeding." *