EFFECTS OF GENOTYPE, SEX AND FEEDING REGIMEN ON PIG CARCASS DEVELOPMENT .1. PRIMARY COMPONENTS, TISSUES AND JOINTS

Dissection data for 1006 pig carcasses taken from the first 2 yr of the Meat and Livestock Commission''s (MLC) Commercial Pig Evaluation (CPE) were used to examine the relationships between carcass components and carcass wt over the growth period from 46-92 kg carcass wt. Alternative models were tested and parameters examined for different genotypes (pigs from different companies in CPE), sexes (barrows and gilts), feeding regimens (ad lib and restricted feeding) and yr. Linear allometry provided an acceptable description of carcass development although some curvilinearity was indicated for the head, kidneys, rump back joint, Musculi psoas and total dissected lean. Growth coefficients conformed to the generally accepted pattern of carcass development in pigs. Using linear allometry proportional wt increases were comparable for all genotypes and sexes, but dissected fat increased relatively faster on the restricted feeding regimen. At a constant carcass wt of 66.5 kg all tissue wt and the wt of primary components and most joints differed by genotype. The ratio of carcass lean wt for the 2 extreme genotypes was 1.04; comparable ratios for carcass fat wt were 1.13 (restricted-fed pigs) and 1.07 (ad lib-fed pigs). Significant differences were recorded between sexes and between feeding regimens largely reflecting differences in fatness; important yr differences were found.