The effect of mixing, feed restriction and genotype with respect to stress susceptibility on pork carcass and meat quality

Abstract

The effects of genotype for stress susceptibility with respect to the halothane gene (PSS genotype: NN = homozygous normal, Nn = heterozygous, nn = homozygous recessive), in combination with fasting and mixing during the 24 h prior to shipping for slaughter upon the carcass traits and quality of the longissimus muscle were investigated using a total of 229 pigs. In comparison to pigs of the NN genotype, pigs of the nn genotype had higher warm carcass yield, cold carcass yield, yield of the major cuts and lean yield of the major cuts by 47, 39, 5 and 15 g kg−1, respectively. Pigs of the Nn genotype had 30 and 8 g kg−1 higher warm carcass yield and yield of major cuts, respectively, than did NN pigs. Pigs of the nn genotype had 178 g kg−1 and pigs of the Nn genotype had 66 g kg−1 more total lean in the major cuts than NN pigs but these differences were not detected by the carcass grading system. Mixing and fasting both caused live-animal weight losses and reduction of warm carcass yield. Fasting had the greater influence, decreasing live animal weight by 54 g kg−1 and the warm carcass yield by 12 g kg−1 in comparison to the unmixed, unfasted pigs. Combined fasting and mixing for 24 h decreased live animal weight by 62 g kg−1 and the warm carcass yield by 19 g kg−1 in comparison to the unmixed, unfasted pigs. Pigs of both nn and Nn genotypes produced poorer muscle quality than did those of the NN genotype. Fasting of pigs for 24 h pre-slaughter alleviated the PSE problem to a small extent. Mixing, with or without fasting, improved muscle quality of pigs of the Nn and nn genotypes. However, such gains in meat quality due to mixing and/or fasting are negated by the decreases in the carcass yield, by the additional carcass damage due to fighting and finally by their possible detriment to animal welfare. Key words: Mixing, fasting, halothane genotype, carcass, pork quality, pigs