Seasonal influence on the reproductive performance of swine in the humid zone of Ghana.

Relationships between month and climatic factors (ambient temperature, relative humidity, RH, and rainfall) with litter size, conception rate, days from weaning to conception and mortalities at birth and preweaning were studied in large white pigs under research station (RS) and commercial farm (CF) conditions. In RS and CF 868 and 572 farrowing records, respectively, were involved. Litter size was almost evenly distributed in all months of the year, at both farms, despite significant (P less than 0.05) negative but low correlations between litter size and maximum (r = -0.272, RS) and minimum (r = -0.233, CF) temperatures in the month after conception. There were no significant differences in conception rate between months. However under RS conditions there were significant (P less than 0.05) correlations between minimum temperature and conception rate in the months prior to (r = -0.362) and at conception (r = -0.221). Days from weaning to conception were bimodally distributed with peak values occurring between January and June and October and December. Significant mortality at birth (P less than 0.05) and preweaning was generally highest in the cold rainy months of May to October. However, only under CF conditions were there significant correlations between minimum temperature in the month of birth and percentage mortalities at birth (r = -0.217) and preweaning (r = -0.250). Rainfall and RH had no significant (P greater than 0.05) correlation with birth and preweaning mortalities.