Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: March 28, 2001
Publication Date: May 20, 2001
Citation: Christenson, R.K., Leymaster, K.A., Ford, J.J., Wise, T.H. 2001. Effects of selection for ovulation rate or uterine capacity on postweaning return to estrus, weaning-to-estrous interval, and postweaning ovulation rate in swine [abstract]. Proceedings Sixth International Conference on Pig Reproduction, Columbia, Missouri, p. 116. (Abstract No. 66) Technical Abstract: The objective of this study was to study correlated responses of selection for ovulation rate (OR) or uterine capacity (UC) on return to estrus, weaning-to-estrous interval, and ovulation rate after weaning in first-litter sows of control (CO), OR, or UC lines. Gilts were mated within line and farrowed in spring (March) or fall (October) seasons during 1998, 1999, and 2000. Litters were allowed to nurse for 16-20 d. At weaning, sow were weighed and moved to group pens. Using mature boars, daily estrous detection was conducted for 14 d after weaning. Sows were slaughtered to confirm estrous activity and ovulation rate. The percent of sows that returned to estrus within 14 d postweaning was significantly greater in the fall (84.5%) than in the spring (70.1%) season. However, a significant (P<.05) line by season interaction indicated that selection for ovulation rate or uterine capacity improved the percent return to estrus in the less favorable spring season but had no effect on the percent return to estrus in the fall season. Means for weaning-to-estrous intervals were longer in CO (spring = 7.0 +/ .2; fall = 6.7 +/ .2 d) than in OR (spring = 6.7 +/ .2; fall = 5.6 +/ .2 d) or UC (spring = 6.3 +/ .2; fall = 6.4 +/ .2 d) sows. Weaning-to-estrous interval was improved in OR sows in both seasons but was significantly improved (P<.01) in the fall season. Weaning-to-estrous interval tended to improve in UC sows but was only significantly (P<.05) improved in the spring season. Postweaning ovulation rate was greater (P<.01) in the OR line than the CO or UC-line sows (18.6 +/ .2 vs 15.0 +/ .3 or 15.0 +/ .3 corpora lutea, respectively). Direct selection for increased ovulation rate and uterine capacity in gilts produced an improvement of postweaning reproduction traits in first-litter sows.