Equine Matters Spring 2019

17 Equine Matters Spring 2019 Moody Mare Managing the Moody Mare Although moody mare behaviour is common in mares under the influence of hormones, it is essential to rule out other non-hormonal causes. Karl Holliman BVM&S CertEP MRCVS Cliffe Equine Vets Mares are seasonal breeders and will come into season (oestrus) and breed during the spring and summer months. Their breeding pattern has evolved to ensure foals are born in the summer, when the ground conditions, grass availability and the weather are at their optimum. During the breeding season mares come into oestrus approximately every 21 days with each season lasting between 3 and 6 days, under influence of the hormone ‘oestrogen’. During this time mares will show typical behaviour of ‘winking’ (opening and closing their vulva), posturing and frequent urination; all to signal to a stallion that they are ready to mate. The presence of high levels of oestrogen causes swelling of the reproductive tract which can cause pain, discomfort and colic in some mares. This ‘mare-ish’ behaviour can make them difficult to ride, handle and groom, often affecting their ability to perform under saddle. Added to this, mares may be more interested in finding a stallion nearby, than concentrating on their rider or handler! During the winter months mares, conversely, enter winter anoestrus where their hormone levels are low, meaning they don’t usually exhibit this mare-ish behaviour. There is a period between the winter anoestrus and the breeding season, known as the transitional phase where mares have a period of erratic cycles of varying length, that can cause prolonged periods of unpredictable behaviour until the normal oestrus cycling pattern establishes. In rare situations, moody mare behaviour may be caused by abnormalities of the ovaries such as the presence of a Granulosa Cell Tumour. With prolonged abnormal behaviour change in a mare, examination of the ovaries with ultrasound and blood samples should be carried out to rule out such tumours. These tumours can grow to very large sizes and may release high levels of sex hormones and can influence behaviour. These are usually non-malignant, and removal of the affected ovary carries a very good prognosis for future breeding. We all have experience of mares that are sweetness and light most of the time and then, seemingly for no reason, turn into teeth baring angry monsters, with no prior warning! These moody mares are difficult to handle and can be impossible to ride. Understanding the cause of this behaviour will help formulate a treatment plan.