Abnormal Mare Behavior is Rarely Associated with Changes in Hormonal Markers of Granulosa Cell Tumors 

A study aimed to determine the association between undesired mare behaviors and concentrations of ovarian hormones associated with a GCT.
Abnormal mare behavior often thought to be associated with hormones can include pinning ears.
According to this study, most abnormal mare behaviors are not associated with increased ovarian hormones. | iStock

Abnormal or undesired mare behaviors are often assumed to be associated with ovarian abnormalities. The aim of this retrospective descriptive study was to determine the incidence of abnormal behaviors and their association with concentrations of one or more ovarian hormones associated with a granulosa cell tumor (GCT).

Is Undesired Mare Behavior Really Associated with Ovarian Hormones?

A total of 2914 hormonal profile samples with the words behave, behavior or behaving in the submission history were analyzed. The association between reported abnormal behaviors and concentrations of testosterone, anti-Müllerian hormone (AMH), inhibins and inhibin-B were assessed. 

Overall, 2506/2914 (86%) cases 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 behavior was significantly associated with increased concentrations of all four hormones. In contrast, aggression, estrous and other abnormal behaviors were significantly less likely to be associated with increased concentrations of the hormones.

Bottom Line

Overall, the abnormal behaviors among mares, except the stallion-like behavior, were not associated with increased ovarian hormones. 


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