a1 Agricultural Research Institute of Northern Ireland, Hillsborough Co. Down BT26 6DR
a2 Department of Food Science, The Queen's University of Belfast, Newforge Lane, Belfast BT9 5PX
a3 Department of Agriculture for Northern Ireland, Newforge Lane, Belfast BT9 5PX
A study was made in two parts to establish the production performance potential of pigs taken to heavy slaughter weights (a) in individual housing and (b) in group housing. In experiment 1 96 crossbred pigs, comprised of equal numbers of boars, castrated males and gilts, were housed individually from 50 kg live weight and offered food ad libitum until one of four target slaughter weights was reached (70, 80, 90 or 100 kg carcass weight). Detailed dissection and meat quality assessments were performed on sample joints taken from these pigs. There were significant interactions in that boars maintained a high level offood conversion efficiency while this deteriorated at heavier weights for castrated males and gilts. Protein deposition rates (PDR) were estimated to be close to, or in excess of, 200 glday for boars. Daily live-weight gains were similar at all four slaughter weights despite increases (P < 0·001) in daily food intake at the heavier weights. Sample joint contents of lean (P < 0·05) and bone (P = 0·001) decreased while subcutaneous fat content increased (P < 0·001) with increasing slaughter weight. Cooking loss was reduced (P < 0·001) at the heavier weights while other meat quality parameters were not significantly affected by slaughter weight or gender. In experiment 2 288 group-housed boars and gilts were slaughtered at the same four target carcass weights as in experiment 1. Daily food intake, daily live-weight gain and variability in performance were lower for group-housed animals. It is concluded that maximum lean growth lies beyond ad libitum food intake for group-housed pigs of the genotype used in the present study. There are opportunities to take pigs to high slaughter weights with no reduction in daily live-weight gain and concomitant improvements in some aspects of meat quality.
(Received March 11 1998)
(Accepted June 18 1998)