Do Mares go through the Menopause?

Mares usually reach an age where they are unable to conceive but this age varies from mare to mare. They usually don't actually go through a menopause int he same sense as humans do (with the cessation of monthly cycles and hormone release). Mares are seasonal breeders so they don't cycle all year round as is the case with humans. 

The pituitary gland and the ovaries release several hormones that are needed to trigger oestrus, ovulation and for the maintenance of pregnancy so if any one of these declines or stops functioning altogether then the mares reproductive ability will also be reduced or cease. 

There are of course other reasons why an older mare may also not conceive, which include disruption of the pH and bacteria level of the vagina, a conformation defect of the vulva, infections, or medical conditions such as endometriosis (where uterine cells grow outside of the uterus such as on the ovaries) or even cysts growing within the lining of the womb.