I am curious about the length of time a horse will breed. Will Z have a foal every year, or does she take time off? What is the average age to retire a broodmare?
A:Thoroughbred mares are usually are not bred before their three-year-old year, and they frequently have foals when they are 21 or 22 years old. The gestation period is about 338 days, plus or minus three or four days.
Mares will usually come into estrous (heat) seven to ten days after foaling. We rarely breed mares during this heat because it does not allow a mare adequate recovery time after foaling, has a low percentage of conception and a slightly higher incidence of fetal loss.
Some mares adapt to motherhood very well and seem to thrive on it, while others do not handle it as well. If everything goes normally a mare will probably be bred on her second estrous cycle after foaling. This occurs at around 27 to 30 days post foaling. There is a high percentage of conception at this cycle and low incidence of fetal loss.
Since the mares’ gestation is more than eleven months, and we don’t breed until 30 days after foaling, they tend to foal a little later each year. Consequently it is difficult for a mare to have a foal every year. Usually, if everything goes normally a mare will have four or five foals and then take, or have, a year off. Occasionally a mare will foal 12 or 13 years in a row, but that is unusual. These mares seem to flourish in a pregnant state.
Mares are weaned at around five to six months after foaling, turned out most of the time weather permitting, and are usually brought in every night about a month before their due date.
Hagyard Equine Medical Institute
Dr. Holder completed his Doctor of Veterinary Medicine at Texas A&M University in 1972. Immediately following, he joined Hagyard Equine Medical Institute as an intern. He has then stayed on with the clinic as a Field Care Associate and then as a Member of the practice. He specializes in Theriogenology, and developed fetal sex determination techniques from 5-150 days.