In season, unsound or unhinged?

Is your mare suffering from a hormone imbalance or is there something else causing that unwanted behaviour? Charlotte Thomas MRCVS investigates

- Charlotte Thomas

OESTRUS, or in-season behaviour, is easy to recognise in some mares. Signs can include frequent urination, squatting, everting the vulval lips toexpose the clitoris (known as winking) and unpredictable and unmanageable behaviour. Oestrus behaviour is a normal manifestation of the mare’s cycling breeding hormone levels throughout the year.

In non-domesticated herds, this behaviour is important to indicate to the stallion when the mare is receptive to covering and when she is at the point most likely to conceive within her cycle. Likewise, in a stud farm scenario, the mare’s responsiveness to a “teaser” (a stallion that is used to test if a mare is ready to be served) is used alongside ultrasound imaging to determine when is the best time to natural cover or artificially inseminate.

In equestrian situations not related to breeding, although this behaviour is not abnormal, it can be unwelcome. Problems can manifest in a subtle loss of performance to a mare that is unrideable when in season.

But are changes in behaviour related to a mare’s seasons? Before embarking on treatment to address unsavoury in-season behaviour, it must be ascertained if the mare’s reproductive system is actually the root of the problem. If the difficult attitude is shown all the way through the mare’s cycle during spring – as well as through the winter when most mares don’t cycle – it is unlikely that her reproductive hormones are the source of the problem. Lameness, back, teeth, gastric ulcers and training issues must be considered alongside hormonal causes.