Effect of confinement, climatic conditions and litter parity on the seasonal variations of the fertility rate and prolificacy.

Prolificacy and fertility in sows were analysed according to the month of service, the regional locations of the herd, the type of building (confinement or open front) and the parity of the sows. Fertility varied throughout the year and was lowest in August, September and October. The regional location of the herd had little or no effect. Primiparous sows were less fertile than multiparous sows, regardless of the type of building. Results for closed buildings were better than those for semi-outdoor quarters. This difference was maximum (8%) for matings in August, September and October. Prolificacy also varied with season but was relatively unaffected by the type of housing. The largest litters were conceived in summer when the ovulation rate was highest. The extend of seasonal variation in prolificacy was higher in Brittany than in the South of France in which hot climatic conditions are more frequent in summer. The month of service and the type of housing appear to be the most important factors conditioning the annual productivity of sows.