Growth characteristics and carcass composition of pigs with known genotypes for stress susceptibility over a weight range of 70 to 120 Kg

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Abstract
A total of 805 Lacombe pigs of different genotype with respect to halothane sensitivity (halothane positive, nn = 205; heterozygote, Nn = 214; halothane negative, NN = 386) were slaughtered over a range in live weight (70 to 120 kg) to assess tissue growth patterns using the allometric equation (y = aXh). The nn genotype was older at slaughter than the NN genotype, but pigs from each genotype were killed over a similar weight range. The relative growth of the primal cuts was influenced by genotype, with nn pigs having a lower coefficient for the bottom shoulder (picnic) and a higher coefficient for the belly. The relative growth of bone was similar for genotypes (P > 0·05) but the relative growth of lean was lower and the relative growth of total fat and depot fat (subcutaneous and intermuscular) was higher for the nn genotype compared with the Nn and NN genotypes. On a within-tissue basis, the relative growth of the tissues in each primal was similar, except for the ham, where the relative growth of lean was higher for nn pigs compared with the two other genotypes. Small differences in tissue distribution were evident, but seldom exceeded 30 g/kg. Although nn pigs had a higher lean content and higher lean: bone ratio than Nn or NN pigs at similar live weights, their relative advantage in composition decreased with increasing live weight.