Elevation of Plasma FSH with a Low Level of FSH-P During the Early to Mid Follicular Phase Blocks the Loss of Greater Numbers of Medium Follicles in Control Line Gilts Compared to Gilts Selected for High Ovulation Rate
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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.