Pet Care
Your Horse and.....Working her in Season
Can I work my mare when she is ‘in season’?
Yes you can! But be understanding of her cycle and try to arrange not to enter events when she is in season. A mare’s oestrus cycle or ‘season’ usually starts in the spring or early summer, when the days become longer than the nights. Owners will find that their mare behaves normally for about seventeen days, but then notice changes for the next three to five days. These changes in behaviour are often described as being ‘difficult’ or ‘naughty’, often called ‘mareish’ behaviour. This is perfectly natural equine behaviour as nature intended. To understand this behaviour better, mare owners should understand the following:
The Equine Oestrus Cycle
The Pituitary Gland releases follicle stimulating hormone (FSH) under the influence of the hypothalamus. (A follicle is a fluid filled sac which develops around an egg in the ovary). FSH causes several of these follicles to enlarge and produce the hormone oestrogen. It is the oestrogen levels that cause the mare to come into season. Once certain oestrogen levels are reached in the blood, the pituitary gland releases luteinising hormone (LH) which reduces the production of FSH and causes just one follicle to mature in the ovary. The ovary eventually ruptures releasing the egg (ovum), this ovulation occurs about 24 hours before the end of oestrus. After ovulation the levels of oestrus drop and the mare goes ‘out of season’. She is now not receptive to a stallion. The empty follicle develops into the corpus luteum which secretes the hormone progesterone. This prepares the uterus for the implantation of the fertilized egg (ovum). However, if fertilization has not occurred the empty uterus will produce the hormone prostaglandin, which stops the corpus luteum from producing progesterone. The pituitary gland responds to this drop in progesterone and stimulates the release of FSH to repeat the cycle once more. It can take between 21 and 22 days for the whole cycle from start to finish. Whilst in season a mare can behave quite differently. Signs of being in season do vary from horse to horse but may include: frequent passing of urine, raising her tail and ‘winking’ her vulva, irritability, stubbornness, and an attraction to a stallion or gelding. .