Reproductive Performance in Domestic Ruminants
Estradiol is a major regulator of the reproductive system in females. When the hypothalamic-pituitary axis is more sensitive to estradiol, females do not exhibit normal estrous cycles. In domestic livestock this occurs during the prepubertal period, postpartum anestrus and seasonal anestrus. Sheep exhibit increased sensitivity to estradiol and exhibit anestrus, or lack of reproductive cycles, during the summer months. Idaho ranks within the top ten states in numbers of sheep (USDA NASS 2008). Furthermore, the greatest numbers of sheep among the United States are within the states associated with the W1112 multi-state project. Although it has been known for decades that estradiol has both positive and negative effects on the hypothalamic-pituitary axis, there are major gaps of information pertaining to how estradiol regulates reproduction at the
anterior pituitary. Success of this project will ultimately be determined by how the results add to or fill-in the gaps of knowledge that currently lacks in how estradiol has multiple effects on a single cell type critical for reproduction. The significance of this research would potentially allow researchers to separate the positive and negative effects of estradiol to control reproductive cycles. These data will not only be pertinent to reproduction of sheep, but also managing reproduction through assisted reproductive techniques in both dairy and beef cattle. Since the actions of estradiol in sheep are similar in cattle it is anticipated that what is discovered upon completion of the proposed experiments should be applicable to cattle as well.