Dietary energy and protein for growing pigs : 2. protein and fat accreation and organ weights of animals slaughtered at 20, 50, 80 and 110 kg live weight

This ivestigation was performed to study to effects of restricted versus ad libitum feeding on carcass composition, on protein and fat accretion and on body development and organ weights. The carcass composition was evaluated on 168 pigs by serial slaugter at 20,50, 80 and 110 kgLW. The chemical composition ws examined in only 62 of these animals. The carcasses were partitioned into four cuts and dissected into lean meat, fatty tissue, rind and bones. Ad libitum feeding resulted in daily weight gain exceeding restricted feeding in te three weight ranges by 42%, 17% and 7% and feed conversion ratios by 3%¬15% and 9%, respectively. Castrated males exceeded daily weight gains of females by 6%. At 20 kg the carcass moisture content was 65% for both sexes, which on averace over feed rgimens at 110 kg decreased to 56%and 52% for females and castrated males respectively. Correspondingly, the carcass crude fat (CF) content increased from 13% to 24% and 30%, respectively. At 110kg LW on restricted feedingthe carcass meat content of females exceeded that of castrated males by 1.7, and on ad libitum feeding by 3.9 prcentage units; corresponding, carcass atty tissue of castrated males exeeded those values for females by 0.5 and 3.9 percentae units, respectively. Daily carcas crude protein (CP) accretion on ad libitum feedig for females and castrated males for the interval 22-111 LW was, on average, 95 g. Daily accretion on ad libitum feeding exeeded that on restricted feeding by 34%. Ad libitum fed castrated males and females showed daily CF accretion rates 0f 231 g and 158 g, respectively. Ad libitum feeding increased weights of liver over restrictd feeding by 12% (p<0.001). Feed regimen also influenced CF content of muscles. It is concluded that feed regimen influenced arcass CP content at slaughter only to a limited extent, but greatly influenced daily CP accretion. However, carcass CF content and daily CF accretion were largely influenced by feed regimen and sex. These differeces became manifest after 50 kg LW. Feed regimen also influenced liver and kidney weights.