Some signs that a mare is in heat, or going through its estrus cycle, include aggressiveness toward other horses, frequent urination, and exhibiting sensitivity or pain in her flanks, according to the American Association of Equine Practitioners. When a mare wrings her tail, she is also displaying heat signals.
The estrus cycle of a mare lasts between 21 and 22 days, explains the American Association of Equine Practitioners. During this time, a mare can exhibit signs of this cycle for between five and seven days. Veterinarians can provide a heat suppressant to reduce the undesirable behaviors linked to a mare’s cycle, including the synthetic progestin Regu-Mate and Depo-Provera. Female horses can experience side effects such as muscle soreness from these suppressants, and some of these treatments require daily administration. Owners should observe a mare’s activity and be sure her behavior isn't linked to other issues before requesting an estrus suppressant.
Determining if a mare is in heat is a significant step in the breeding process because it is vital in natural and artificial breeding, notes eXtension. Heat detection involves discovering if a mare is sexually mature. A mare displays interest in stallions during her estrus cycle, and she has a higher chance of conception during this time, but these signs are unpredictable. Breeders can use the process of teasing to determine if a mare is in heat by observing how she reacts to a stallion.