Threshold dose of estradiol for inducing sexual receptivity in ovariectomized French-Alpine goats

The minimum dose required, i.e., threshold dose, of estradiol (E₂) for inducing receptivity in ovariectomized goats was determined. Ovariectomized French-Alpine goats were treated with doses of E₂ ranging from 20 to 40 μg during exposure to either ambient breeding season conditions or to constant 8L:16D artificial photoperiod conditions. Beginning 17 h following injection of E₂, behavioral observations were conducted in the presence of sexually-experienced male goats. Five out of 6 goats housed in 8L:16D and 6 out of 7 housed in ambient conditions displayed receptivity after receiving 30 μg of E₂. The number of goats displaying receptivity following treatment with 20 μg of E₂ was not significantly different than those receiving vehicle. Therefore, the minimum effective dose of E₂ for stimulating receptivity under either environmental condition was 30 μg.