Animal Science Department


Date of this Version



Published in 1995 Nebraska Swine Report, edited by Duane Reese; published and copyright © 1995 Animal Science Department, University of Nebraska – Lincoln.


The number of follicles ovulated (ovulation rate) at estrus is an important determinant of litter size in the pig because it sets the upper limit for litter size.

Ovulation rate is a moderately heritable trait in pigs (h2 = 40%). Gilts selected for high ovulation rate (Relax Select, RS line) in the University of Nebraska Gene Pool population ovulated about 3.5 more follicles than randomly selected Control (C) line gilts after nine generations of selection. This difference continues to be maintained after many generations of random selection following the end of deliberate selection.