Estrus, ovulation, and serum hormones in mares given prostaglandin F2 alpha, estradiol, and gonadotropin-releasing hormone.

The research involves attempting to synchronize ovulation in horses using prostaglandin F2 alpha and gonadotropin-releasing hormone injections. It also investigates whether pretreatment with estradiol influences the release of the luteinizing hormone.

Research Design and Methods

• The research was based on an animal model, using twelve mares in a balanced Latin square crossover design. This design allows for the testing of multiple treatments and control conditions to minimize potential bias or variations influencing the results.
• Three different treatments were applied to the mares. Treatment A involved an injection with prostaglandin F2 alpha (PGF2 alpha), a substance known to induce luteolysis or the breakdown of the corpus luteum, a structure involved in ovulation and early stages of pregnancy. Treatment B included PGF2 alpha in conjunction with gonadotropin-releasing hormone (GnRH), which is crucial to the regulation of reproductive hormones. Finally, Treatment C consisted of PGF2 alpha, estradiol-17 beta (E2-17 beta), and GnRH. Estradiol is a form of estrogen; it was part to test its potential to augment luteinizing hormone (LH) release after GnRH treatment.

Research Findings and Interpretations

• The onset of estrus (a period of sexual receptivity in female mammals) after injection varied slightly across treatments, being shortest for Treatment C. However, the interval between injection and first ovulation was slightly shorter for treatments B and C compared to treatment A.
• The duration of estrus and the interval from ovulation to end of estrus were similar for all three treatment groups, implying the treatment did not significantly impact these aspects.
• Significant increases in the LH concentrations were noted in mares given GnRH (treatments B and C), suggesting that GnRH can effectively stimulate LH production. However, pretreatment with estradiol-17 beta did not appear to further enhance LH release after GnRH was administered. Thus, the use of E2-17 beta might not be beneficial in the context of this treatment.
• The time of ovulation was not significantly impacted by GnRH treatment, meaning it did not lead to a method to effectively synchronize ovulation in mares.

Conclusion

• Overall, the research sheds light on the effects of different hormone injections on the reproductive cycles in mares. It points to the potential effectiveness of GnRH in increasing LH concentrations but also indicates that estradiol-17 beta might not enhance this effect. Moreover, the study did not find a reliable way to synchronize ovulation using these treatments.
• Despite these findings, more research may be necessary to further understand specific mechanisms, other possible treatments, and their effects on horse reproduction.