Effect of halothane genotype (NN, Nn, nn) on growth, carcass and meat quality traits of pigs slaughtered at 95 kg or 125 kg live weight

A total of 446 F2 Pietrain x Large White pigs of the three halothane genotypes NN, Nn and nn, as determined by a DNA-based test for the ryanodine receptor gene, were reared on ad libitum feeding and slaughtered either at 95 kg or at 125 kg live weight. Growth performance, carcass composition, and meat quality were studied, to assess the dominance-recessiveness of the n allele and its possible evolution with increasing slaughter weight. Average daily gain was significantly lower (by 23 g/day) in nn than in NN and Nn pigs, whereas the food conversion ratio was only slightly affected by the halothane genotype. Carcass yield and lean to fat ratio significantly increased from NN to Nn and from Nn to nn genotype, with Nn being intermediate. For carcass lean percentage and killing-out percentage, the difference between nn and NN pigs was estimated at 3.5 +/- 0.4% and 1.1 +/- 0.2%, respectively, and the dominance effect did not significantly differ from zero for both traits. Pigs from nn genotype showed, to a highly significant extent, a lower pH 45 min, higher L*-values, an inferior water-holding capacity, and a higher muscle lactate content than pigs from NN genotype. For pH 45 min and L*-value, the dominance effect differed from zero, with Nn pigs being significantly closer to NN than to nn pigs. Conversely, there was a trend toward Nn pigs being closer to nn than to NN pigs for water-holding capacity. The halothane genotype had no significant effect on ultimate pH, muscle glycolytic potential, and a meat quality index predicting the curing-cooking yield of ham processing. No evidence for major interaction between slaughter weight halothane genotype was found. However, the difference between Nn and NN tended to decrease when slaughter weight increased.