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Animal reproduction science2008; 115(1-4); 88-102; doi: 10.1016/j.anireprosci.2008.11.011

Suppression of testicular function and sexual behavior by vaccination against GnRH (Equity) in the adult stallion.

Abstract: The aim of this study was to evaluate the effects of an anti-GnRH vaccine on testosterone concentration, antibody titer, scrotal width, semen quality and sexual behavior in the stallion. Adverse reactions to the vaccine were also determined. Eight clinically healthy sexually experienced stallions aged between 6 and 15 years from the National Stud in Avenches (Switzerland) were used. Five stallions were immunized 3 times at an interval of 4 and 8 weeks, respectively, with 200 microg of a GnRH-protein conjugate (Equity, CSL Limited, Australia) intramuscularly in the neck and 3 control animals received an equivalent volume of saline solution. Plasma testosterone concentrations and GnRH antibody titers as well as semen quality and libido were determined weekly during 1 year (52 weeks). In addition, scrotal width was measured in all stallions before and 4, 8 as well as 12 months after first vaccination. Our results demonstrate that in 4 stallions plasma testosterone started to decrease after the second vaccination and remained suppressed for at least 6 months whereas one stallion showed no effect. Until the end of the experiment 2 stallions reached prevaccination testosterone values. Antibody titers varied individually in all 5 stallions and reached peak concentrations within 2 weeks after the third vaccination. Scrotal width was significantly (P<0.05) lower in vaccinated than in control stallions 8 months after first vaccination. Semen quality started to decreased after the second vaccination and improved towards the end of the experiment. In 4 stallions libido was clearly reduced after the second immunization but normalized in 2 animals before the end of the study while 2 stallions continued to show poor libido. From our results we conclude that three immunizations with Equity are well tolerated in the stallion and may effectively suppress testosterone secretion and reduce semen quality as well as sexual behavior. The inhibiting activity of Equity on these parameters is individually different and may last for a minimum of 6 months.
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Publication Date: 2008-11-20 PubMed ID: 19128902DOI: 10.1016/j.anireprosci.2008.11.011Google Scholar: Lookup
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Summary

This research summary has been generated with artificial intelligence and may contain errors and omissions. Refer to the original study to confirm details provided. Submit correction.

The research explores the impact of an anti-GnRH vaccine, used on adult stallions, on testosterone levels, sexual behavior, semen quality, and other associated parameters. It was found that the vaccine had effects for a minimum duration of six months, suppressing testosterone production, reducing semen quality, and altering sexual behaviors.

Study Design and Participants

  • The study involved eight healthy, sexually experienced stallions aged between 6 and 15 years belonging to the National Stud in Avenches, Switzerland.
  • Five of these stallions were subject to three immunizations with 200 micrograms of a GnRH-protein conjugate vaccine (Equity) while the remaining three stallions served as the control group, receiving saline solution instead.
  • The vaccinations were administered intramuscularly in the neck at intervals of 4 and 8 weeks.

Research Methodology

  • The researchers evaluated multiple aspects for more than a year – plasma testosterone concentrations, GnRH antibody titers, semen quality, sexual libido, and scrotal width.
  • Scrotal width was measured before the vaccination and again after 4, 8, and 12 months.

Results

  • In four of the stallions vaccinated, there was a decrease in plasma testosterone beginning after the second vaccination, which remained suppressed for at least six months. However, one out of the five vaccinated stallions showed no such effect.
  • Antibody titers reached peak concentrations within two weeks after the third vaccination, with variations observed among the stallions.
  • There was a significant decrease in scrotal width in the vaccinated stallions as compared to the control group, eight months after the first vaccination.
  • Semen quality too started decreasing post the second vaccination but saw an improvement towards the end of the experiment.
  • Libido was visibly reduced in four of the vaccinated stallions after the second immunization, although it gradually normalized in two of these animals by the end of the study.

Conclusion

  • The study concludes that the use of the Equity vaccine in stallions is generally well tolerated.
  • It effectively suppresses testosterone production, reduces semen quality, and alters sexual behavior for a minimum duration of six months.
  • However, the inhibiting activity of the vaccine on these parameters differed among individual stallions.

Cite This Article

APA
Janett F, Stump R, Burger D, Thun R. (2008). Suppression of testicular function and sexual behavior by vaccination against GnRH (Equity) in the adult stallion. Anim Reprod Sci, 115(1-4), 88-102. https://doi.org/10.1016/j.anireprosci.2008.11.011

Publication

Animal reproduction science
ISSN: 1873-2232
NlmUniqueID: 7807205
Country: Netherlands
Language: English
Volume: 115
Issue: 1-4
Pages: 88-102

Researcher Affiliations

Janett, F
  • Clinic for Reproductive Medicine, University of Zürich, Winterthurerstrasse 260, CH-8057 Zürich, Switzerland. fjanett@vetclinics.uzh.ch
Stump, R
    Burger, D
      Thun, R

        MeSH Terms

        • Animals
        • Antibody Formation
        • Ejaculation
        • Female
        • Gonadotropin-Releasing Hormone / immunology
        • Gonadotropin-Releasing Hormone / pharmacology
        • Horses
        • Luteinizing Hormone / antagonists & inhibitors
        • Luteinizing Hormone / immunology
        • Male
        • Ovariectomy
        • Penile Erection
        • Semen / physiology
        • Sexual Behavior, Animal / drug effects
        • Sexual Behavior, Animal / physiology
        • Sperm Count
        • Spermatozoa / abnormalities
        • Spermatozoa / drug effects
        • Testis / drug effects
        • Testis / physiology
        • Testosterone / blood
        • Testosterone / immunology
        • Vaccines / adverse effects
        • Vaccines / pharmacology

        Citations

        This article has been cited 17 times.
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