Effect of the halothane gene on pre-slaughter mortality in two Spanish commercial pig abattoirs

A total of 107 ear samples from all the pigs that died during transport or lairage at two commercial abattoirs were collected during two months (February, and July), in order to determine their halothane genotype (NN, Nn or nn). The frequencies of the three halothane genotypes among dead pigs were significantly, different (P < 0.001), being 4.7%, 24.3% and 71.0% for NN, Nn and nn individuals, respectively. The frequencies of pre-slaughter deaths within each genotype were estimated to be 0.02%, 0.09% and 2.29% for NN, Nn and nn genotypes, respectively. According to these results, the removal of both nn and Nn genotypes would give rise to an eleven-fold reduction in the pre-slaughter mortality, rate (from 0.22% to 0.02%). It is therefore suggested that, from an animal welfare point of view, the elimination of the halothane gene in existing breeding schemes would have a major beneficial impact.