To successfully deal with an abnormal mare you must understand the normal heat cycle, particularly the part about transitional phases during early spring and fall. For an overview of the normal heat cycle see the article Breeding Patterns in Mares under the Reproduction Menu. This article deals with some of the causes for abnormal heat cycles, particularly the mare who will not come into heat or go out of heat.

Besides transitional periods, another important concept about normal mares are that they all do not act the same. The behavior you observe, may have little to do with the stage of the breeding cycle the mare is in. Yes, most mares, when out of heat will squeal, swish and clamp their tails, and pin their ears when exposed to a stallion. Yes, most mares, three to five days prior to ovulation are receptive, squat and squirt urine, and do not attempt to kick the stallion. But, some normal mares don't. They may be unusually nervous and squirt urine at the drop of a hat or unusually aggressive and will kick the stallion in the hottest part of the heat.

When I say normal, I mean they are cycling physiologically (they are ovulating, forming a corpus luteum which regresses in about 14 days if not pregnant and then follicles begin to mature etc.). The behaviorally abnormal mares either do not act like they are in heat close to ovulation, or do not act like they have gone out of heat after ovulating. These mares will settle if bred at appropriate times. These type mares need aggressive daily teasing and an observant handler who will notice slight changes to indicate when she really is in estrus. Usually clues will be there if you are watching and taking notes. These mares act the same, cycle after cycle and year after year. Good written records are a must.

If you just can't tell, have the veterinarian check the mare: a simple manual exam of the cervix will answer the question: is she in? You can learn to do this yourself with help from the vet. A series of rectal exams, by an experienced vet, two to three days apart will help answer whether she is cycling normally.