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Equine veterinary journal2023; doi: 10.1111/evj.13967

Abnormal mare behaviour is rarely associated with changes in hormonal markers of granulosa cell tumours: A retrospective study.

Abstract: Abnormal or undesired mare behaviours are often assumed to be associated with ovarian abnormalities. Objective: We aimed to determine the incidence of abnormal behaviours and their association with concentrations of one or more ovarian hormones associated with a granulosa cell tumour (GCT). Methods: Retrospective descriptive. Methods: A total of 2914 hormonal profile samples submitted with the words behave, behaviour, or behaving in the submission history were analysed. The association between reported abnormal behaviours and concentrations of testosterone, anti-Müllerian hormone (AMH), inhibins and inhibin-B were assessed. Statistical analysis was performed using a Chi-squared test of association. Results: Of the 2914 cases that were submitted due to behaviour issues, 2506 (86%) did not have any of the measured hormones reach GCT-like concentrations. The remaining 408 cases had either one (63%), two (25.5%), or three (11.5%) hormones with concentrations consistent with those from confirmed GCT cases. Testosterone had the lowest percent of GCT-like values among the cases (7.7%), compared with AMH (9.4%), inhibins (9.6%) and inhibin B (8.7%). Stallion-like behaviour was significantly associated with increased concentrations of all four hormones. In contrast, aggression, oestrous and other abnormal behaviours were significantly less likely to be associated with increased concentrations of the hormones. Conclusions: Retrospective study, using sample submission history. Conclusions: Overall, the abnormal behaviours among mares, except the stallion-like behaviour, were not associated with increased ovarian hormones. These results highlight the common misassumption about the involvement of the ovaries in 'abnormal behaviours' or 'undesirable behaviours' of mares.
© 2023 The Authors. Equine Veterinary Journal published by John Wiley & Sons Ltd on behalf of EVJ Ltd.
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Publication Date: 2023-06-21 PubMed ID: 37344926DOI: 10.1111/evj.13967Google Scholar: Lookup
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Summary

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This research investigates the relationship between abnormal behaviour in mares and hormonal changes linked to granulosa cell tumours (GCTs), a type of ovarian tumour in horses. The study concludes that abnormal equine behaviour, with the exception of stallion-like behaviour, is typically not associated with elevated levels of ovarian hormones, challenging the common belief that ovarian abnormalities play a significant role in abnormal or undesirable behaviour in mares.

Methodology

The researchers conducted a retrospective study of 2914 samples of mares’ hormonal profiles. These samples were specifically chosen because they were submitted with reports of abnormal behaviour. Using these samples, the team investigated the correlation between behavioral issues and the levels of the hormones testosterone, anti-Müllerian hormone (AMH), inhibins and inhibin-B.

  • A retrospective approach was used to investigate the relationship between abnormal behaviour in mares and levels of the four hormones mentioned.
  • The behavioral issues that led to the mares’ hormonal profiles being examined were noted with terms such as ‘behave’, ‘behaviour’, or ‘behaving’.
  • The researchers used the Chi-squared statistical test to evaluate the relationship between abnormal behaviours and hormone concentrations.

Results

The results indicated that of the 2914 cases of reported abnormal behavioural issues:

  • 86% (2506 cases) showed no GCT-like concentrations of any of the examined hormones.
  • Of the remaining 408 cases, 63% had one hormone, 25.5% had two hormones, and 11.5% had three hormones with concentrations consistent with GCT cases.
  • Testosterone had the lowest percent of GCT-like values (7.7%) compared to AMH (9.4%), inhibins (9.6%) and inhibin B (8.7%).
  • Stallion-like behaviour was significantly linked with increased concentrations of all four hormones.
  • Aggression, oestrus functions, and other abnormal behaviours were significantly less likely to have high levels of the hormones.

Conclusion

In conclusion, the research found that, besides stallion-like behaviour, abnormal behaviours in mares are generally not related to high levels of ovarian hormones. This contradicts the common belief that ovarian abnormalities are a key cause of undesirable behaviours in mares. The outcomes underline the importance of eschewing assumptions in the medical diagnosis of abnormal behaviours.

Cite This Article

APA
Huggins L, Norris J, Conley A, Dini P. (2023). Abnormal mare behaviour is rarely associated with changes in hormonal markers of granulosa cell tumours: A retrospective study. Equine Vet J. https://doi.org/10.1111/evj.13967

Publication

Equine veterinary journal
ISSN: 2042-3306
NlmUniqueID: 0173320
Country: United States
Language: English

Researcher Affiliations

Huggins, Lauren
  • Department of Population Health and Reproduction, School of Veterinary Medicine, University of California, Davis, California, USA.
Norris, Jamie
  • Department of Population Health and Reproduction, School of Veterinary Medicine, University of California, Davis, California, USA.
Conley, Alan
  • Department of Population Health and Reproduction, School of Veterinary Medicine, University of California, Davis, California, USA.
Dini, Pouya
  • Department of Population Health and Reproduction, School of Veterinary Medicine, University of California, Davis, California, USA.

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Citations

This article has been cited 3 times.
  1. Derar D, Ali A, Al-Sobayil F, Refaai W. Granulosa cell tumor in Arabian mares: prevalence, risk factors, clinical and histopathological findings and outcome of surgical removal. Front Vet Sci 2025;12:1689782.
    doi: 10.3389/fvets.2025.1689782pubmed: 41321570google scholar: lookup
  2. Wolf N, Hahn JA, Walter I, Zablotski Y, Zerbe H, Witte TS. Pathohistological Findings after Bilateral Ovariectomy in Mares with Behavioral Problems. Animals (Basel) 2024 Oct 8;14(19).
    doi: 10.3390/ani14192899pubmed: 39409848google scholar: lookup
  3. 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).
    doi: 10.3390/vetsci10080483pubmed: 37624270google scholar: lookup
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