Submitted to: Journal of Animal Science Supplement
Publication Type: Abstract Only
Publication Acceptance Date: May 30, 2000
Publication Date: June 1, 2000
Citation: Leymaster, K.A., Christenson, R.K. 2000. Direct and correlated responses to selection for ovulation rate or uterine capacity in swine. [abstract]. Journal of Animal Science. 78(Suppl. 1):68.
The objective was to estimate responses of ovulation rate (OR), uterine capacity (UC), and litter size (LS) to selection for either OR or UC in a four-breed composite population of swine. A replicate of each OR, UC, and control (CO) line was established in two seasons (A and B). During the selection phase of the experiment, OR at the estrus of conception was recor ron dams of line OR. In line UC, UC per uterine horn was measured as numbe fully-formed pigs born to unilaterally hysterectomized-ovariectomized (UHO) dams. Boars and gilts from OR and UC dams with the greatest records were selected for 11 generations. Then, to remove accumulated inbreeding effect prior to evaluation of responses, generation 11 replicate A gilts were mate to generation 10 replicate B boars and generation 11 replicate B gilts to generation 11 replicate A boars. Resulting littermate gilts of each line w randomly assigned to either remain intact for observation of OR and LS or t tundergo UHO surgery for observation of OR and UC. Direct selection for OR effective (3.21 ova, P<.001), however, correlated responses in UC (-.11 pig per uterine horn) and LS (.70 pigs) were not detected. Likewise, direct selection for UC increased UC by 1.11 pigs per uterine horn (P<.01), althou correlated responses in OR (-.01 ova) and LS (.92 pigs) were not detected. These responses established that OR and UC were heritable and genetically independent of one another. Using published equations based on the OR-UC model of LS, observed and predicted LS means were 10.62 and 10.50 pigs for line CO, 11.32 and 11.69 pigs for line OR, and 11.54 and 11.04 pigs for lin UC. Simultaneous increases in both OR and UC are necessary to produce a substantial increase in LS.