When is the Best Time to Breed Your Mare?

Written By: Pat Griffin, DVM, PhD, DACT

Written By: Pat Griffin, DVM, PhD, DACT

This is the time of year when owners are finalizing plans to breed their mares in the coming spring. A frequently asked question is “When is the best time to breed my mare?” The answer is dependent on a number of factors, including the goals you have as a mare owner (e.g. an “early” baby for show/sale reasons), the reproductive status of your mare (foaling, maiden, barren or aged or problem mare), stallion availability and his fertility, foaling facilities (including options for turn-out of mare and foal) and your geographic location (frigid Midwest vs. more temperate climates).

Goal = Early Foal

Remember that mares are “long day” breeders in nature, with regular reproductive cycles tied to increasing hours of daylight as the spring progresses. In order to hasten the transition to regular cyclicity earlier in the spring, we recommend exposing your mare to 14-16 hours of light per day, beginning around December 1st. This is vital when your goal is to have a foal hit the ground in January or February the following year. Our preference is to then perform a complete ultrasound exam on these stimulated mares around the first of February to assess their status (cycling, transitional, non-cyclic or anestrous) and initiate any therapies necessary to facilitate regular cycles. If your mare has not been stimulated by an artificial lighting regimen, chances are that she will not be cycling regularly until later in the spring when the days lengthen naturally. The time she initiates regular cycles in the spring is also influenced by her age and body condition.  Once we’re certain your mare has had her first ovulation of the year, we’re ready to breed.

Foaling Facilities and Weather

Another consideration in breeding for an early foal is the availability of adequate facilities for foaling and turnout late in the winter or early in the spring. If viable options are not available, it’s probably best to wait to breed until later in the spring when the weather is more forgiving and hospitable to mare and foal during the stressful period surrounding foaling the subsequent spring. Obviously, this consideration is less important the more temperate the climate in your location.

Mare’s Reproductive Status

Consideration of your mare’s reproductive status will also influence the best time to breed her. If she is a foaling mare, we prefer to examine her around 6-7 days post-foaling to identify any issues that may have arisen during foaling and to determine if she is a candidate for a “foal-heat” breeding (i.e., breed on 1st cycle post-foaling). If no issues are identified, we do not hesitate to breed her back on the foal heat. If the mare does not meet our criteria or has had a difficult foaling, or if frozen semen is going to be used, we’ll “short-cycle” the mare off her foal heat ovulation and breed on subsequent heats.

If your mare is a barren mare (i.e. is not a maiden mare, is non-pregnant and has had no foal in the previous year or years) or a “problem”  or aged mare, our recommendation would be to get as early a start as possible in the season to give us as many cycles as necessary to get her in foal before it gets too late in the year.  It is not unusual to breed these types of mares a number of times (2-3 cycles) before we get them going and can get and keep them in foal.

Stallion Considerations

If your stallion-of -choice is actively showing or performing, a determination of his availability and collection schedule during the show and breeding season is crucial and may dictate when your mare is bred.  If we have this information, we can easily manipulate your mare’s cycles to coordinate her breeding times with stallion/semen availability.  Particularly for breedings early in the season, we would also like to know that a stallion has been “cleaned-out” and has been evaluated prior to using his semen, particularly on a cooled, shipped basis.  If he hasn’t been collected and evaluated, it may be best to delay breeding your mare to allow time for him to begin to be bred/collected on a regular basis, maximizing semen quality.

Other factors to consider include the stallion’s age, his fertility and the number of mares he will breed.  In this regard, many older stallions or stallions booked to a large number of mares will have some drop in their fertility as the season progresses and it may be best to breed to them early in the season to maximize chances of a pregnancy.  As well, when breeding to a stallion with fertility issues, it’s important to get an early start on your mare to maximize the number of cycles during which we can breed her in anticipation of a low per cycle pregnancy rate due stallion factors.


There are a number of considerations to think about when deciding when to breed your mare. Work with your local veterinarian to determine what’s the best path moving forward. You can contact us at Irongate Equine Clinic to talk about reproductive services, and what may suit your mare best.

Have questions? Contact us today.