LITTER SIZE AND PRE- AND POST-WEANING PERFORMANCE IN SWINE

Analysis of performance data from 209 barrows and 222 gilts, representing 135 gilt litters, indicated an important inverse relationship between litter size at birth and weaning and individual pig weights at both ages. Differences in litter size at weaning had no measurable influence on the post-weaning traits of average daily gain during the weight-constant growth period of 50 to 195 ± 3 pounds or on the carcass traits of length and loin area. There was reasonably consistent evidence of a small effect on total back fat, with females from small litters producing a greater amount of fat than expected in relation to their contemporary test barrows. These relationships were confirmed by analysis of a further sample of 149 barrows and 147 gilts from 82 litters. The significance of these findings in relation to R.O.P. testing is discussed briefly.