Influence of immunization against GnRH on reproductive cyclicity and estrous behavior in the mare.
Abstract: The aim of this study was to evaluate the effect of active immunization against GnRH on ovarian activity, plasma progesterone and estradiol concentrations and on estrous behavior in adult mares. Eighteen cyclic mares were randomly divided into a treatment and control group. Nine mares were immunized twice with 2 mL (400 microg GnRH-protein conjugate) of a GnRH-vaccine (Improvac, CSL Limited, Australia) administered intramuscularly, 4 weeks apart. Control mares received the same amount of saline solution. Ovaries and uterus of all mares were examined weekly by ultrasonography from 3 weeks before to 60 weeks after first immunization. Thereafter, vaccinated mares were evaluated monthly until 100 weeks after first vaccination. In addition, mares were teased with a stallion for assessment of estrous behavior and blood was collected for progesterone, estradiol-17beta and GnRH antibody titer determination. Results demonstrate that vaccination against GnRH significantly (P<0.05) influenced all parameters, except estradiol-17beta concentration. All vaccinated mares ceased reproductive cyclicity (plasma progesterone <1 ng/mL, follicles 3 cm, progesterone >1 ng/mL) while three mares showed only follicular activity (follicles >3 cm) and one mare remained completely suppressed for the entire duration of the study. In spite of ovarian suppression, four mares expressed sporadic and one mare continuous estrous behavior. In conclusion, reproductive cyclicity in adult mares can be successfully suppressed by immunization against GnRH but the timing of resumption of cyclicity is highly variable and estrous behavior may occur in spite of ovarian suppression.
Publication Date: 2006-06-15 PubMed ID: 16780942DOI: 10.1016/j.theriogenology.2006.04.038Google Scholar: Lookup
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- Journal Article
Summary
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This research article investigates the effects of immunization against GnRH (a hormone) on the reproductive cycle and estrous behavior in mares. It illustrates how the vaccine disrupts typical ovarian activity, progesterone levels, and reproductive behaviors while leaving estradiol levels mostly unaffected.
Research Methodology
- The study involved eighteen adult mares that were divided into two groups: a control group and a treatment group, each consisting of nine mares.
- The mares in the treatment group received two immunization injections of a GnRH-vaccine (Improvac), four weeks apart. In contrast, the control mares were given a saline solution equal to the amount of the vaccine used for the treatment group.
- From three weeks prior to the first immunization to sixty weeks afterwards, all mares’ ovaries and uterus were examined weekly via ultrasonography. Post the sixty-week phase, only the vaccinated mares were evaluated on a monthly basis until 100 weeks after the first vaccination.
- Estrous behavior was monitored by teasing the mares with a stallion, and blood was collected for determining progesterone, estradiol, and GnRH antibody levels.
Key Findings
- The findings from the research showed that the GnRH vaccine substantially affected all the observed parameters, except for estradiol concentration.
- Within eight weeks of receiving the first injection, all immunized mares stopped their reproductive cycle. The ovarian activity remained suppressed for at least 23 weeks.
- Out of the nine vaccinated mares, five resumed their reproductive cycle, three demonstrated only follicular activity, while one mare remained entirely suppressed for the duration of the study.
- Interestingly, even though ovarian suppression was achieved, four mares exhibited sporadic estrous behaviors, and one mare demonstrated continuous estrous behavior.
Conclusion
- The study concludes that it’s possible to suppress reproductive cyclicity in adult mares via GnRH immunization.
- However, the timing of resumption of the cycle varies significantly among individuals. Moreover, estrous behavior may still be observed despite ovarian suppression.
Cite This Article
APA
Imboden I, Janett F, Burger D, Crowe MA, Hässig M, Thun R.
(2006).
Influence of immunization against GnRH on reproductive cyclicity and estrous behavior in the mare.
Theriogenology, 66(8), 1866-1875.
https://doi.org/10.1016/j.theriogenology.2006.04.038 Publication
Researcher Affiliations
- National Stud, Avenches, Switzerland.
MeSH Terms
- Animals
- Estradiol / blood
- Estrus / blood
- Estrus / drug effects
- Estrus / physiology
- Female
- Gonadotropin-Releasing Hormone / immunology
- Gonadotropin-Releasing Hormone / pharmacology
- Horses / blood
- Horses / physiology
- Immunization / veterinary
- Injections, Intramuscular / veterinary
- Ovulation / drug effects
- Ovulation / physiology
- Progesterone / blood
- Random Allocation
- Reproduction / drug effects
- Reproduction / physiology
- Sexual Behavior, Animal / drug effects
- Sexual Behavior, Animal / physiology
Citations
This article has been cited 9 times.- Stachurska A, Kędzierski W, Kaczmarek B, Wiśniewska A, Żylińska B, Janczarek I. Variation of Physiological and Behavioural Parameters during the Oestrous Cycle in Mares.. Animals (Basel) 2023 Jan 6;13(2).
- Botha AE, Schulman ML, Birrell J, du Plessis L, Laver PN, Soley J, Colenbrander B, Bertschinger HJ. Effects of an anti-gonadoliberin releasing hormone vaccine on testicular, epididymal and spermatogenic development in the horse.. Reprod Domest Anim 2022 Aug;57(8):919-927.
- Aurich C, Kaps M. Suppression of reproductive behaviour and gonadal function in female horses-An update.. Reprod Domest Anim 2022 Sep;57 Suppl 4(Suppl 4):4-12.
- Schwarzenberger F, Krawinkel P, Jeserschek SM, Schauerte N, Geiger C, Balfanz F, Knauf-Witzens T, Sicks F, Martinez Nevado E, Anfray G, Hein A, Kaandorp-Huber C, Marcordes S, Venshøj B. Immunocontraception of male and female giraffes using the GnRH vaccine Improvac®.. Zoo Biol 2022 Jan;41(1):50-64.
- Kawase K, Tomiyasu J, Ban K, Ono R, Ando S, Ono A, Kimura R, Tomisawa K, Matsui M, Shiihara SI. Contraceptive effect of a gonadotropin-releasing hormone vaccine on a captive female African Lion (Panthera leo): a case study.. J Vet Med Sci 2021 Sep 15;83(9):1454-1458.
- Baker DL, Powers JG, Ransom JI, McCann BE, Oehler MW, Bruemmer JE, Galloway NL, Eckery DC, Nett TM. Reimmunization increases contraceptive effectiveness of gonadotropin-releasing hormone vaccine (GonaCon-Equine) in free-ranging horses (Equus caballus): Limitations and side effects.. PLoS One 2018;13(7):e0201570.
- Hirsbrunner G, Rigert S, Janett F, Hüsler J, Schnydrig P, Lopez E, Amatayakul-Chantler S, Steiner A. Immunization against GnRF in adult cattle: a prospective field study.. BMC Vet Res 2017 Jul 1;13(1):208.
- Hermes R, Schwarzenberger F, Göritz F, Oh S, Fernandes T, Bernardino R, Leclerc A, Greunz E, Mathew A, Forsyth S, Saragusty J, Hildebrandt TB. Ovarian down Regulation by GnRF Vaccination Decreases Reproductive Tract Tumour Size in Female White and Greater One-Horned Rhinoceroses.. PLoS One 2016;11(7):e0157963.
- Benavides Valades G, Ganswindt A, Annandale H, Schulman ML, Bertschinger HJ. Non-invasive assessment of the reproductive cycle in free-ranging female African elephants (Loxodonta africana) treated with a gonadotropin-releasing hormone (GnRH) vaccine for inducing anoestrus.. Reprod Biol Endocrinol 2012 Aug 25;10:63.
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