A comparison of seasonal effects on fertility of Landrace and Large White sows in a subhumid tropical environment

Forty sows comprising equal numbers of Landrace (LR) and Large White (LW) breeds were studied for 20 months to determine the effects of dry and rainy seasons on their fertility traits in Nigeria. Ambient temperature (14·0–35·5 °C) was lowest at night and highest in the day and peaked during the dry season. A relative humidity range of 60–82% peaked during the late rainy season. LR produced 218 and 278 piglets from 23 and 28 litters, while LW produced 193 and 316 piglets from 20 and 30 litters during dry and rainy seasons respectively. Fertility traits did not differ significantly between the breeds due to season ( P > 0·05). Mean post-weaning oestrus at 10·9 and 9·0 days and preweaning mortality rates of 14·2% and 16·9% during dry and rainy seasons for LR differed significantly ( P < 0·5) from those of LW which were 12·2 and 8·2 days and 14·5% and 18·9% respectively. The significance of seasonal effects on sow fertility and necessary management techniques are discussed.