Peripheral plasma levels of progesterone in goats treated with fluorogestone acetate and prostaglandin F2 α during the estrous cycle

Abstract

Intravaginal pessaries impregnated with 20 mg fluorogestone acetate (FGA) were inserted into fifteen does at various intervals after the end of estrus. After resumption of cyclical activity following withdrawal of the intravaginal pessaries, the does were divided into six groups and treated with prostaglandin F2 α. Each doe received 15 mg Prostaglandin F2 α administered intramusuclarly 2, 4, 6, 12, 14 or 16 days after the end of estrus. The animals were bred naturally on the first estrus following prostaglandin treatment. Jugular blood samples were collected from each doe throughout the experimental period. The plasma samples were assayed for progesterone. Intravaginal fluorogestone acetate treatment in does had no effect on the function of the corpus luteum, however, overt estrus was postponed during treatment and for a few days after removal of the pessaries. Prostaglandin injection into does, 4, 6, 12, 14 or 16 days after the end of estrus induced luteolysis and subsequent ovulatory estrus within 2 to 3 days. Fertility at PGF2 α induced estrus in these does was 77%. Prostaglandin treatment two days after the end of estrus had no effect on the corpus luteum function. It is concluded that prostaglandin is luteolytic when administered into does anytime beyond four days after the end of estrus.