Sows were weighed individually at placement (110 ± 2 d of gestation) and at weaning (22 ± 2 d). Sow BW at farrowing was estimated assuming 0.7-kg daily gain from the day of placement to the day of farrowing based on a daily ME intake of 8 Mcal (Close et al., 1984) minus litter weight at birth, which included pigs born alive,stillborn pigs, and mummifi ed pigs, and the estimated
weight of the placenta and fluid (Noblet et al., 1985). Sow growth rate was calculated as the difference between BW at weaning and estimated BW at farrowing divided by the number of days of the lactation period. Back fat and loin depth were measured in a subset of 328 sows at day 112 ± 2 of gestation and at weaning using realtime ultrasound (PigLog 105, SFK-Technology, Herlev,
Denmark). Measurements were taken at 2 points on the sow: between the 9th and 10th ribs, 10 cm from the midline,and between the 3rd and 4th vertebrates of the spine,10 cm from the midline of the sow. These points of measurement were identified with a red marker on each sow so that measurements were made at the same location at both time points to minimize variation between sampling.