A genetic study of cryptorchidism and scrotal hernia in pigs.

The genetic parameters of cryptorchidism and scrotal hernia were estimated. The heritability of liability to cryptorchidism identified at birth was about 0.5 and that identified to be normal at birth, but recognized to be abnormal later was almost zero. The heritabilities of scrotal hernia estimated in two herds were 0.65 and 0.86. The genetic correlation between these two defects was 0.20. An equation for calculating selection differentials for family selection was derived and expected changes of incidence resulting from individual, full-sib and half-sib family selection calculated. Practical culling plans were discussed from the aspect of selection response and possible culling rate.