Factors affecting the gestation period of pigs in Nigeria.

Gestation periods taken from 432 records on purebred Large White, Duroc, Hampshire and their crossbred sows at Fashola Stock Farm in the Oyo State of Nigeria were analysed to determine the effects of some factors on the trait. For Large White, Duroc, Hampshire and the crossbred sows the mean gestation periods were 113.2, 115.1, 114.5 and 112.8 days respectively. Overall least squares mean was 11.2 days with a standard deviation of 9.06 days. Litter size at birth, year of birth and breed x season interaction had very highly significant effects of length of pregnancy. Breed differences were significant (P less than 0.05) whereas parity and season per se did not seem to influence this trait. Effects of boars accounted for some 11.8% of the trait was estimated as 0.47 r - 0.20 while the repeatability coefficient was 0.13. The data indicated a slight negative association between gestation period and litter size at birth.