Genetic parameters and halothane genotype effect for residual feed intake in Piétrain growing pigs

Data were collected in the frame of the French pig breeding scheme for the Piétrain breed in which the halothane sensitivity allele (n) is segregating. This data set was used to estimate: (1) genetic parameters for residual feed intake (RFI) and growth, body composition and meat quality traits and (2) effect of the three halothane genotypes on these traits. Individual feed intake of animals raised from 35 to 107 kg body weight in collective pens (12 animals maximum) was recorded using single-place electronic feeders. A total of 2312 animals were tested between 2002 and 2009 in three French central test stations: 176 were homozygous non-sensitive (NN), 470 were heterozygous (Nn) and 1666 were homozygous sensitive (nn) for the halothane locus. Variance components were estimated using the REML methodology applied to a multitrait animal model, including a random litter effect and, for meat quality traits, a random slaughter day effect. RFI showed a moderate heritability (0.40 ± 0.06), similar to the estimate for feed conversion ratio (FCR, 0.47 ± 0.07), with a genetic correlation of 0.85 ± 0.04 between these traits. Pairwise contrasts between halothane genotypes showed that the halothane genotype did not affect RFI, contrary to FCR (P < 0.01 for all pairwise contrasts). We conclude that, in the Piétrain breed, improving feed efficiency by selecting for lower RFI would improve FCR and reduce daily feed intake with limited impacts on growth rate and carcass traits. Moreover, it is not expected to modify the frequencies of the halothane alleles in the population, contrary to selection for reduced FCR.