Inhibition of ovulation in the mare by active immunization against LHRH.
Abstract: To investigate the hypothesis that the onset of the breeding season in the mare may be due to a daylength-induced seasonal increase in LHRH pulse frequency, 5 mares were immunized against LHRH. Beginning 1 December, 5 immunized and 5 untreated control mares were exposed to an abrupt, artificial increase in daylength (16L:8D) to advance the onset of the breeding season. In control mares ovulation occurred 49.6 +/- 3.5 (s.e.m.) days later (18 January), whereas in 3/5 immunized mares ovulation had not occurred by 1 April. In the remaining 2 mares, although ovulation occurred once (Mare 79) or twice (Mare 72) during February, a booster immunization restored acyclicity for the duration of the study (No. 72) or to 30 March (No. 79). The absence or occurrence of ovulation in LHRH-immunized mares appeared to be related to antibody titre, such that the highest antibody titres were observed in those mares that remained anovulatory throughout the experimental period, while low titres were seen in the 2 mares that ovulated. In 3 acyclic immunized mares, LH pulses were not observed in blood samples collected frequently at 2-week intervals from November to January. In contrast, LH pulse frequency in control mares, and in the 2 immunized mares that ovulated, increased from 0/12 h (November) to 2-5/12 h (January). These results confirm our previous observation that, in the mare, the onset of the breeding season is associated with an increase in LH pulse frequency. Furthermore, the results suggest that the increase in LH pulse frequency reflects an increase in pulsatile LHRH release from the hypothalamus.
Publication Date: 1987-01-01 PubMed ID: 3316639
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- Journal Article
- Research Support
- Non-U.S. Gov't
Summary
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The research article investigates the effect of LHRH immunization on mares. It suggests that the breeding season’s onset may be regulated by a natural increase in LHRH levels, and that suppressing these through LHRH immunization, prevents ovulation.
Objective of the Study
- The primary objective of the research was to explore the theory that the onset of the breeding season in mares could be attributed to an increase in Luteinizing Hormone-Releasing Hormone (LHRH) pulse frequency triggered by seasonal daylength changes. The study aimed to analyze this by actively immunizing mares against LHRH and observing its effects on ovulation.
Methodology
- The study was conducted on 5 mares who were actively immunized against LHRH. Alongside, the mares along with five untreated controls were exposed to an artificially extended daylength (16 hours light : 8 hours dark) from December 1st to simulate the augmentation of breeding season.
- The frequency of ovulation was tracked, with specific attention to if and when ovulation occurred. The same was monitored for the untreated control mares.
- The experiment also included booster immunizations and careful observation and recording of changes in LHRH antibody titers in the immunized mares.
- In addition to the ovulation tracking, LH pulses were observed in the blood samples collected from the acyclic immunized mares at two-week intervals.
Results
- The study found that ovulation in control mares occurred around 49.6 days after the artificial increase in daylength, i.e., around 18th of January. However, more than half of the LHRH immunized mares remained non-ovulatory until the 1st of April, well beyond the common ovulation period of the control mares.
- A correlation was noticed between ovulation and LHRH antibody titres; higher antibody titres corresponded with non-ovulatory mares, while the mares with lower titres were seen to ovulate.
- In the mares that did not cycle, LH pulses in blood samples were non-detectable, unlike in control mares and the immunized mares that ovulated, where LH pulse frequencies increased from November to January.
Conclusion
- The findings validated the initial hypothesis drawn by the researchers that the onset of the breeding season in mares is influenced by an increase in LH pulse frequency which is in turn may be reflective of an increase in pulsatile LHRH release from the hypothalamus.
- Additionally, it was inferred that introducing LHRH immunization in mares can influence this process, chiefly by inhibiting or delaying ovulation.
Cite This Article
APA
Safir JM, Loy RG, Fitzgerald BP.
(1987).
Inhibition of ovulation in the mare by active immunization against LHRH.
J Reprod Fertil Suppl, 35, 229-237.
Publication
Researcher Affiliations
- Department of Veterinary Science, University of Kentucky, Lexington 40546-0076.
MeSH Terms
- Animals
- Female
- Gonadotropin-Releasing Hormone / immunology
- Gonadotropin-Releasing Hormone / physiology
- Horses / physiology
- Immunization / veterinary
- Luteinizing Hormone / blood
- Ovulation
Citations
This article has been cited 2 times.- Straticò P, Hattab J, Guerri G, Carluccio A, Bandera L, Celani G, Marruchella G, Varasano V, Petrizzi L. Behavioral Disorders in Mares with Ovarian Disorders, Outcome after Laparoscopic Ovariectomy: A Case Series. Vet Sci 2023 Jul 25;10(8).
- Meloen RH. Basic aspects of immunomodulation through active immunization. Livest Prod Sci 1995 Jun;42(2):135-145.
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