Selection for uterine capacity improves lifetime productivity of sows

Selection for 11 generations for uterine capacity (UC) increased litter size in gilts by 1.6 more fully formed pigs at birth compared to an unselected control line (CO) despite averaging one less ovulation. The objective of the present study was to quantify line by parity interactions and characterize litter performance traits of sows in each line at later parities. Gilts farrowed in contemporary groups of 19 litters and were maintained through four parities if successfully mated in that contemporary group. A total of 243 litters and 2639 piglets were analyzed. Fixed effects of farrowing group, line, parity (1-4), and two-way interactions involving line were fitted. Sire (n=57) of the sow within farrowing group and line was fitted as a random effect. No significant line by parity interactions were observed. Parity effects were detected (P<0.01) for individual piglet birth weight, pre-weaning gain, and weaning weight. Parity effects were also detected (P<0.05) for total number born, average and total litter birth weight, and average and total litter weaning weight. Selection line differences for litter traits were detected (P<0.05) for number stillborn piglets and approached significance (P=0.06) for number of piglets weaned. Retention of sows in the herd was greater (P<0.05) with an average of 2.33 parities for the UC line females compared to 1.87 parities for the CO line. This resulted in favorable cumulative lifetime productivity of the UC line for total number of piglets born, number of piglets born alive, litter birth weight, number of piglets weaned and litter weaning weight.