By April, equine breeding season is in full swing and today we are going to talk about equine breeding beginning with the estrus cycle. Most mares are classified as being seasonally anestrus, which means that they cycle at certain times of the year. In the case of mares, they cycle when days are longer in the spring and summer and most stop cycling in the late fall and winter. Because we like foals to be born early in the year, it is possible to manipulate mares to begin cycling earlier in the spring by placing them in a stall under artificial lights from November to February. The mare's normal cycle is 21 days from one ovulation to the next. The mare is in heat usually about 1 week of the cycle and usually ovulates toward the end of the heat period. Dr. David Hartman in the 2009 Remuda Magazine indicates mares that have shorter cycles than normal could have a uterine infection. Mares that have longer cycles than normal could have cysts in the uterus, or could have been pregnant and the pregnancy died before it was even noticed.

It is important that all mares should be examined by your veterinarian prior to breeding, especially maiden mares and those that have had problems getting pregnant in the past. A complete breeding soundness exam is really worth the money in problem mares and this includes a biopsy of the uterus, a culture of the uterine contents as well as a cytology, which is an exam of cells in the uterus. Also, the cervix should be examined to see if it is functioning correctly as many mares do not get pregnant because of cervical problems. Be sure and join us on our next program when I will discuss more about equine breeding.