Whether you show, breed or do both, the mare management is the same: You want to control when your mare comes into heat. Tools such as shipped semen and embryo transfer have made equine reproduction a logistical and biological equation. Getting a mare in foal the first time, at the right time, is more critical than ever. Performance mares are also expected to perform consistently at a very high level. If your mare’s behavior changes when she’s in heat, she may be a candidate for hormone management.
How hormone suppression works
As a mare enters estrus and prepares for breeding, her levels of estrogen rise. After ovulation, estrogen drops and is replaced with an increasing amount of progesterone. Progesterone prepares her uterus for pregnancy and prevents abortion of the fetus. Roughly 14 to 16 days after ovulation, if the mare is not pregnant, her progesterone levels decline and the cycle starts over.
Regu-Mate® (altrenogest) is a form of progesterone that can help you reliably mange your mare’s estrous cycle. When given daily for up to 15 consecutive days, Regu-Mate reliably keeps mares from entering estrus. When use of Regu-Mate is discontinued, mares will come into heat within 4 to 5 days.
Managing the breeding mare with hormones
There’s nothing more gratifying for a breeder than a promising new foal hitting the ground healthy. A successful outcome starts months prior with the initial breeding, and identifying the time of ovulation is crucial for a successful outcome.
There are a variety of tools available to help take some of the guesswork out of breeding, including hormone treatment. Most breedings will result in conception when they occur 24-36 hours before ovulation or the day of ovulation.
Mares transitioning from winter anestrus to normal cycling often experience irregular and erratic cycles. Progestin hormones combined with 60 days of artificial lighting have the highest success rate in inducing normal estrus sooner.
Whether you want to ensure your mare is ready when the transported semen arrives, breed multiple mares at once or get donor and recipient mares on the same schedule, there are many benefits to scheduled breeding. The timing between treatment and ovulation should be more consistent with normally cycling mares than with transitional mares.
The first estrous cycle after a mare foals may not be the most fertile. Suppressing the cycle and allowing more time for the uterus to involute and return to normal can increase conception rates. Delaying ovulation as little as four days can result in a significantly higher conception rate.
The use of altrenogest to suppress estrus in order to facilitate scheduled breeding requires a veterinarian’s prescription and consultation. He or she can accurately predict ovulation and help you more efficiently manage your breeding program.
Managing the performance mare with hormones
If you’ve ever used the term “bad mare day,” you know the frustrations that can come with showing a mare in heat. Many trainers of performance mares opt to control the estrous cycle using hormone therapy.
Signs of a mare in heat:
- Tail flagging
These behaviors are demonstrated by mares while in estrus for five to eight days during the 21-day cycle and are mediated by the hormone estrogen. If this period of time corresponds with performance or critical training activities, undesirable estrous behavior can be distracting. Elimination of this estrous behavior is naturally accomplished after a mare ovulates and estrogen is replaced with the hormone progesterone, which is produced by the mare’s ovaries during diestrus.
This result can be duplicated with altrenogest. Within three days of the start of treatment, Regu-Mate will effectively suppress estrus in 95% of mares.When use of Regu-Mate is discontinued, mares will return to estrus, or come into heat, within four to five days.
It’s important to note altrenogest cannot improve your mare’s normal performance, it can only eliminate hormonal distractions so she can focus and perform more predictably.
Whether your goal is breeding or performance, your best resource for mare management is your veterinarian. Click here for more information on Regu-Mate.
Learn the language
Time when a mare is in heat and receptive to stallions. Usually lasts 5 to 7 days. Estrogen is the primary hormone.
Time when a mare is out of heat. Usually lasts 14 to 16 days. Progesterone is the primary hormone.
Time when mare ceases all ovarian activity and is unable to conceive. During the winter months, 80 percent of mares experience anestrus.
Time between winter anestrus and normal estrous cycles, usually February to March. Cycles during this period are erratic and may or may not include ovulation.
Synthetic progesterone hormone, such as Regu-Mate (oral altrenogest).
 Regu-Mate (altrenogest) product label.
 Regu-Mate (altrenogest) product label.