Open mares are costly to most horse breeders. Mares may be open due to late foaling, unsuccessful breeding, or loss of a foal during pregnancy. The key to optimizing your success with broodmares is careful planning and preparation for the breeding season.
One of the many challenges for broodmare owners is getting mares to cycle for early season breeding. In nature the increased hours of daylight occurring in late spring and summer stimulate the transition of a mare's heat cycle from anestrus (not cycling) to regular, active estrus (coming in heat). Approximately 80 - 90% of mares do not naturally cycle in the winter. In the spring they go through a transitional period, which involves irregular heat cycles. It is difficult to get mares in foal during the transitional period. In late spring or early summer they finally settle into a normal 21 day heat cycle that regularly produces follicles that will ovulate.
Fortunately for people that want to breed in the late winter or early spring, we can manipulate the mare's hormones so it is possible to breed early in the year. The easiest and most economic way to achieve this is the use of artificial lights.
Starting around Thanksgiving your mares should be exposed to 16 hours of light per day. This can be any combination of natural and artificial light. The dark phase is also important, so she should have 8 hours of darkness. The intensity of artificial light needed is a 100 watt light bulb in a 12x12 stall. You should be able to read a newspaper in the darkest corner of the stall.
I achieve this by turning my mares out in the natural light in the morning (around 8 am). In the evening I bring them in before dark and start artificial light (around 4 pm). I have a timer that turns off the lights after 8 hours (around midnight). A dark period should not interrupt the transition from daylight to supplemental light and the lighting program should be consistently followed each day. Even 1 or 2 days off schedule can interfere with the mare's cycle. It is wise to confirm that your lighting system is working properly once you have it set up.
Mares that are pregnant with an early foaling date should also be put under lights. This encourages them to continue to cycle after the foal heat.
This is also a good time of year to have your veterinarian check the reproductive health of any open broodmares. Mares should be examined for fluid or cysts in the uterus. A culture and cytology should be performed to identify any possible infections and give ample time for treatment if necessary. A Caslick's surgery can be performed if needed.
Some problematic mares are consistently more difficult to get in foal. You can increase the success rate and save valuable time by having mares ready to breed early as opposed to starting your preparations during breeding season.
If you are breeding to an outside stallion, make sure that you have your breeding contracts finalized and fully understand any semen ordering requirements. The stallion owner should have all payment and shipping information in advance of any orders.
From advanced preparation to breeding work to foaling out, the doctors at Conley and Koontz Equine Hospital provide services to optimize the success of your breeding program. Please feel free to contact us for scheduling or additional information.
Ron Conley, DVM