The effects of genotype, sex and feeding regimen on pig carcass development: 1. Primary components, tissues and joints

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Abstract
Dissection data for 1006 pig carcasses taken from the first 2 years of the Meat and Livestock Commission's (MLC) Commercial Pig Evaluation (CPE) were used to examine the relationships between carcass components and carcass weight over the growth period from 46 to 92 kg carcass weight. Alternative models were tested and parameters examined for different genotypes (pigs from different companies in CPE), sexes (barrows and gilts), feeding regimens (ad libitumand restricted feeding) and years.Generally, linear allometry provided an acceptable description of carcass development, although some curvilinearity was indicated for the head, kidneys, rump back joint, M. psoas and total dissected lean. Growth coefficients conformed to the generally accepted pattern of carcass development in pigs. Using linear allometry, proportional weight increases were comparable for all genotypes and sexes, but dissected fat increased relatively faster on the restricted feeding regimen.At a constant carcass weight of 66·5 kg, all tissue weights and the weights of primary components and most joints differed by genotype. The ratio of carcass lean weights for the two extreme genotypes was 1·04; comparable ratios for carcass fat weights were 1·13 (restricted-fed pigs) and 1·07 (ad libitum-fed pigs).Significant differences were recorded between sexes and between feeding regimens, largely reflecting differences in fatness. Some important year differences were also found.