Effect of Estradiol-17β on Follicular Development and Pituitary Potency in Gilts Fed 6-Methyl-17-Acetoxyprogesterone

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Abstract
Forty Yorkshire and Duroc gilts received approximately 500 mg. of MAP per day orally beginning on day 13 of their respective estrual cycles and continuing for 12 days. An intravenous injection of 10 mg. of estradiol-17β 3 days before slaughter at 4, 7, 10, 13, or 16 days after MAP withdrawal in half of the gilts (four on each day) had no significant effect on gonadotropic potency, follicular development, or the occurrence of estrus, ovulation, or luteinization of follicles. Follicular fluid weight and the average diameter of the four largest follicles increased significantly from 4 to 16 days after MAP withdrawal in both estradiol-treated and untreated gilts, with large cystic follicles being present at days 13 and 16. Although luteinization of follicles occurred in a large number of gilts and follicle size increased, neither FSH nor LH concentrations, nor relative total FSH potency changed during the experimental period, and neither FSH nor LH was significantly correlated with the ovarian changes within groups The correlation between FSH and LH concentrations was 0.52. Copyright © 1963. American Society of Animal Science . Copyright 1963 by American Society of Animal Science