Sex ratio in litters of domestic pigs (Sus scrofa f. domestica Linnaeus, 1758)

The offspring sex ratio is a subject of considerable interest from both the theoretical and the practical point of view. In domestic animals, including pigs, the offspring sex ratio is also a feature of economic value. The gilts from litters with a higher proportion of females can deliver and feed more piglets as they have more teats, a higher fertility rate, and a better reproductive performance. The aim of this paper was to assess whether litter size, maternal age and parity, paternal breed, maternal birth year and month, and litter birth year and month influenced the offspring sex ratio in domestic pigs. A total of 436 litters on 21st day of life were considered. It was found that paternal breed and litter size significantly affected the offspring sex ratio (fewer males in larger litters). Also maternal month of birth had a significant influence on offspring sex ratio (sows born in September-February delivered litters with a higher male proportion than those born in March-August). There was also a correlation at a marginally significant level between the offspring sex ratio on 21st day of life and proportion of stillborn piglets (more stillborn ones in the litters with the future higher male proportion).