Ovarian activity and hormonal patterns in gilts fed allyl trenbolone.

A study was conducted to establish the profile of reproductive hormones and the degree of ovarian activity in gilts fed either 2.5 or 15.0 mg of allyl trenbolone (AT) daily. Progesterone levels following regression of corpora lutea remained low (less than 1 ng/Ml) during progestin treatment. In gilts given 2.5 mg AT, plasma estradiol (E2) levels fluctuated between 7 and 13 pg/ml during treatment and began to decrease by day 2 after withdrawal of AT. Gilts given 15 mg of AT had lower (P less than .01) plasma concentrations of E2 (2.5 pg/ml) during treatment; concentrations began to increase the day after withdrawal of AT, reaching a maximum of 13.1 pg/Ml in 3.5 to 4.0 days. Luteinizing hormone (LH) levels were low (less than 1.5 ng/ml) during AT treatment. Daily feeding of AT prevented estrus in all gilts. A preovulatory surge of LH (4 ng/ml) was observed on the first day of the first post-treatment estrus. Gilts given 2.5 mg of AT daily had more (P less than .01) follicles of ovulatory size during treatment and a higher frequency of cystic follicles after withdrawal than gilts given 15 mg of AT daily. Estrus was effectively synchronized in gilts given 15 mg of AT daily, whereas the feeding of 2.5 mg AT daily resulted in an increased incidence of anestrus.