Factors affecting the number of teats in pigs.

The factors that affect the number of teats in pigs are of interest for both biological and practical reasons. Previous work indicates that there is a genetic component, principally from the dam. The proportion of males in a litter appears to be related to the anogenital distance of the gilts in the litter, possibly as a result of the intrauterine position effect. The present study investigated whether litter size, litter sex ratio, anogenital distance, crown-rump length, distance from base of skull to base of tail, and the number of teats on the dam and boar affected the number of teats on gilts. Stepwise multiple regression on litter mean values (adjusted r2 = 0.178) indicated that two factors were significant: the number of teats on the dam (standard coefficient 0.311) and the proportion of males in the litter (standard coefficient -0.282). A greater number of teats on the dam and a lower proportion of males in the litter resulted in a greater number of teats on the gilt. When the analysis was run using individual gilts as the independent units (adjusted r2 = 0.073), the number of teats on the dam (standard coefficient 0.207), the proportion of males in the litter (standard coefficient -0.135), and the weaning weight of the gilt (standard coefficient 0.083) were all significant predictors of the number of teats. This evidence suggests that teat number in female pigs is related to the proportion of males in the litter.