Effects of season and breed on sow performance in the seasonal-equatorial climate of Southern Nigeria

Abstract

Preweaning litter traits of 289 Large White (LW) and of 167 Landrace (LR) litters born between 1 January, 1967 and 31 December, 1969 were analysed for seasonal effects. The month during which farrowing occurred exerted highly significant effects on the average piglet weight at birth and at weaning, as well as on the preweaning piglet weight gain (P <0·001). Piglet weight at birth was higher during the hot and dry months of the year, while the preweaning piglet weight gain was greater during the cooler season. The heaviest piglets at weaning were those born in August, the coldest month of the year. Piglet weight at birth was negatively correlated with the mean relative humidity of the month of farrowing (r = -0·79; P <0·01). The percentage of stillborn piglets was high in litters born during March and April (P < 0·005), and the positive correlation between the mean physiologically effective temperature and the percentage of stillborn piglets (r = +0·57) approached significance (P < 0·10).The considerable variations in litter size and litter weight at birth and at weaning as well as the variations in preweaning mortality were not significant.The two breeds differed significantly (P < 0·005) in piglet weight at birth (LW: 2·8 lb; LR: 3·0 lb), in litter weight at birth (LW: 24 lb; LR: 28 lb), and in the percentage of stillborn piglets (LW: 4·5%; LR: 7·5%).