An Analysis of Some Factors Affecting Performance in a Large Pig Herd: Annual Production of Pigs Per Sow

Abstract

SUMMARY An investigation into some factors affecting production in a large pig herd is reported. Use was made of records covering a period of 3½ years. A significant seasonal difference was found for stillbirth rate. No seasonal effects were found for total litter size at birth, pre-weaning mortality or returns to service. A significant seasonal difference in birth-weight was found in some cases only. The breed of sire had a significant effect on litter size, stillbirth rate, pre-weaning mortality and percentage of pigs born above 2.5 lb. in weight. No significant breed effects were found for the average birth-weight. The individuality of the sire was the cause of significant variations in litter size, stillbirth rate, pre-weaning mortality, percentage of pigs born above 2.5 lb. in weight and returns to service. No significant sire effects were found for the average birth-weight. A high rate of returns to service was present in both young and old boars. It is suggested that the sire may affect the viability of his offspring, not only during pregnancy but also after birth, by a mechanism independent of both litter size and birth-weight.