Further observations on the relative influence of birth weight and creep-feed consumption on the 3- and 8-week weights of sucking pigs

1. Data from the first 3 litters of each of 21 Wessex Saddleback sows were analysed on within-Utter, between-litter/within-sow and between-litter/ between-sow bases. 2. There were highly significant differences between sows in the mean weight of their pigs at birth, 3 and 8 weeks of age; between litters of the same sow there were no significant differences at birth or 8 weeks but pigs in third litters were significantly lighter than those of the first and second Utters at 3 weeks of age. There was a significant increase in number born but not in number weaned from first to third litters. 3. Within litters, the variation in 3-week weight accounted for by variation in birth weight was 30% in first litters, 48% in second litters and 45% in third; respective relationships between birth weight and 8-week weight were 14, 27 and 26%. Between litters of the same sow, differences in mean birth weight accounted for 50 % of the difference which occurred in 3-week weight and for 26 % of the difference in 8-week weight. Differences in mean creep-feed consumption accounted for 18% and differences in mean 3-week weight for 44% of the differences which occurred in weight at weaning. Between litters of different sows, the variation in birth weight accounted for 48% of the variation in 3-week weight, and 8% of the variation in 8-week weight. Differences in creep-feed consumption accounted for 36% and differences in 3-week weight accounted for 26 % of the difference in weight at weaning. 4. Season of birth had some effect on weaning weight due in part to an effect on creep-feed consumption. There was a negative correlation between birth weight and mortality and a positive correlation between mortality and Utter size.