The inheritance of a tail abnormality associated with urogenital disorders in pigs

Abstract

An analysis of the breeding of 130 kinky-tailed pigs of Large White and Wessex origin indicates that the character is genetic in nature and is of variable penetrance and expressivity. The hypothesis is put forward that pigs, in general, may be charcterized by a slight tendency to this defect which is exhibited when the appropriate accidents of development occur. In addition, there may be genes which raise the overall frequency and severity of the defect. In the Large White inbred strain studied, it is thought that there were minor genes with a recessive effect as well as a major gene with incomplete dominance. In the inbred strain several litters were obtained which included no normal pigs although both parents were apparently normal. In outcrosses, kinky tails appeared less frequently. Inbred, kinky-tailed pigs were difficult to rear and of those kept for breeding most proved sterile. Post-mortem examination of a number of affected pigs showed a high incidence of abnormalities of the kidneys, ureters and genitalia. The suggestion is made that kinky tails are but a minor manifestation of an early developmental disorder.