Many owners report severe behavioural and management problems linked to the oestrous cycle ranging from poor performance to being unmanageable. It is important to establish whether the unwanted behaviour is actually hormone related, or if it could be due to pain or a schooling/behavioural problem.
If the problem is directly relating to oestrous then the behaviour should be seen for 4-7 days out of every 21 day cycle (can be more frequent in spring transition) and should stop in winter. The behaviour should also be abolished by Regumate (a synthetic progesterone) which prevents the mare from coming into season. We often use a trial period of this hormone to establish if there is a hormonal component to the issues you are having. We also do an ultrasound examination of the reproductive tract to ensure there are no reproductive abnormalities.
Once we have established that your mare’s issues are genuinely due to normal oestrous cycles then there are a variety of treatment options;
1) Regumate is the gold standard to prevent your mare coming into season but is relatively expensive for long term use. It can be cost effective if used intermittently for important events.
2) Intrauterine marbles are effective in about 50% of mares and are inexpensive. The marble is inserted through the cervix when the mare is about to ovulate and the marble mimics a pregnancy in the uterus.
3) Intrauterine peanut oil inserted 10 days after ovulation has a similar success rate to marbles. This was found in a study done in 2011. No side effects have been documented and like the marble it is inexpensive. We will be using this treatment this year.
4) ‘Double dose’ Ovuplant (an ovulatory drug) will increase the time between ovulations but works out at a similar price to Regumate which is more effective.
5) Ovary removal is a drastic option but the solution for some owners. Although occasionally mares can maintain oestrous behaviour due to hormones from the adrenal gland!
6) Mare supplements will occasionally help some mares but their effect is limited so unless there is a noticeable change when your mare is on the supplement then it is probably not worth continuing.