THE DEVELOPMENT OF A HALOTHANE-SENSITIVE LINE OF PIGS

Abstract

A halothane-sensitive line of pigs was developed from a Pietrain-Lacombe synthetic line through selection of breeding stock based on their sensitivity to a 4 min, 4.5% halothane challenge. It appears that halothane sensitivity is inherited by a single, autosomal recessive allele (n), that is essentially fully penetrant (0.98) in halothane-sensitive pigs (nn). The gene was fixed within four cycles of selection. Segregation at the halothane locus among the two sexes provided no evidence to suggest differential mortality between the sexes and fit inheritance patterns typical of an autosomal locus. However, litters that originated from nn × nn mating types had 1.3 fewer pigs weaned per litter than those mating types in which at least one parent carried the halothane gene. There was no evidence for any expression of halothane sensitivity in normal pigs (NN) and only infrequent expression in the heterozygote (Nn). Key words: Halothane gene, inheritance, swine