Sexual behavior, seminal pH and accessory sex gland weights in geldings administered testosterone and(or) estradiol-17 beta.

The study explored how administering testosterone and/or estradiol-17 beta affected sexual behavior, seminal pH, and the weight of accessory sex glands in castrated stallions. It found that testosterone restored libido and ejaculation, while estradiol only restored libido. Testosterone or a combination of both hormones lowered seminal pH levels and increased the weight of seminal vesicles, ampullae, and prostate.

Methodology

• Sixteen stallions participated in this research. They were castrated and allowed to heal for 30 days before commencing with the study.
• The stallions were then split into four groups. Each group followed a different treatment plan. The first group was given testosterone propionate, the second was administered 17 beta-estradiol-3-benzoate, the third got a combination of both steroids, and the fourth group served as a control and did not receive any steroids.
• All dosages were delivered every other day over 18 days, then the dosages were doubled and the experiment continued for another 20 days.

Findings

• The concentration of testosterone and estradiol in the blood decreased quickly following castration but became stable in about 6 hours.
• Libido and the ability to ejaculate reduced gradually after castration. Within two weeks of testosterone treatment, these traits were restored.
• Higher doses of estradiol also restored libido, but was less successful in restoring the ability to ejaculate.
• The pH value of semen increased after castration but was reduced by administering testosterone, or a combination of testosterone and estradiol. Estradiol alone had no effect on seminal pH levels.
• The weights of the seminal vesicles, ampullae, and prostate were greater in those treated with testosterone, or both hormones, compared to those treated with estradiol or the control group.

Conclusion

• The research suggests that estradiol might be involved in maintaining libido in intact stallions. This could result from estradiol secreted directly by the testes or from peripheral tissue aromatization.
• The experimental treatment with estradiol at either concentration did not seem to influence the size or function of the geldings’ sex glands.