Not having a mare in optimal condition to conceive results in lower fertility, frustration, and financial losses. Consistent, successful breeding of mares requires planning and attention to detail.
To ensure the mare is cycling regularity, she needs to be at a body condition score (BCS) of 5 or 6 (on a scale of 1 to 9) and be exposed to increasing day length starting 2 to 2.5 months before her breeding date. Mares with a BCS of 5 or 6 cycle earlier, have better fertility, and seem to respond better to artificial lighting schedules. Mares that are thinner (BSC 3 or 4) can also have reasonably good fertility provided they are gaining weight. Mares under natural conditions start cycling between mid-March and May. A supplemental lighting program needs to be started by early in December if the desired breeding date is in February. If the goal is a March or April foal, begin the light treatment in January. Once started, the lighting program needs to be maintained until the natural day length is adequate, or mare may stop cycling. The current recommendation of 14.5 to 16
hours of continuous light a day is easy and highly effective. The supplemental light is added in the evening, which generally means the lights need to be on till 9:30 to 11:00 p.m. Automatic timers are simple to install and help ensure sufficient and consistent lightening. The rule of thumb for light intensity is being able to read a newspaper comfortably, from anywhere in the stall. This roughly translates to a 200-watt incandescent bulb, two standard 40-watt fluorescent tubes, or the equivalent in compact fluorescents. If the mare likes to hang her head outside the stall door, then the aisle also needs to be lit. There are some drugs, such as sulpiride, that can help augment the onset of cyclicity in mares that are slower to respond to lights. Treatment periods of several weeks to a month can be needed, so plan accordingly. Pregnant mares that are due to foal before mid April should also go under lights to ensure they cycle after giving birth. Some caution should be exercised when lighting mares due to foal in early January, especially if your breed society enforces a January 1st birth date. The 60 days of light exposure may shorten pregnancy by up to a week.
Mares that failed to conceive or aborted last season should have been examined to determine the cause of infertility. Future fertility is negatively affected by infection during the offseason. Removing the infection several months before breeding also allows residual inflammation in the uterus to reduce, returning her uterine environment to optimum before the season commences. A complete veterinary exam can check not only for infection, but also for injuries and anatomic defects that affect fertility. Diagnostic methods for these mares include palpation, ultrasound, vaginoscopy and swabbing, but may also involve vaginal and cervical palpation, uterine lavage, biopsy and endoscopic examination of the uterus. Older mares with signs of Equine Cushing's disease or metabolic syndrome should be tested, and necessary treatments or dietary modifications began at least 2 months prior to breeding; this time is necessary to return to optimum fertility.
Many stallion owners will require a negative uterine culture (pre-breeding swab) on all open mares before they are accepted for breeding or semen shipment. Check the breeding contract for timing and requirements; most need to be performed within 30 to 60 days of the first service. Maintenance healthcare including hoof care, vaccinations, deworming, and preventative dental work should also be reviewed and updated several weeks before breeding.