Equine Breeding
by Ben J. Character, DVM
Even as this article is being posted, the equine breeding season is revving up. May and June are the prime months for the natural cycle of the mare. Most mares will be at their best for accepting and maintaining a conception during this time.
Most mares spend January, February, and March breaking out of the anestrus phase and transitioning into a period of strong estrus (“in heat”). This is a result of increasing daylight period after the winter solstice. The only way to change this natural process is to provide artificial light to produce longer periods of daylight, and induce the mare’s body to start producing the hormones that bring forth the transition period and start of estrus. Unfortunately, there is no magic medicine that will create this effect and bring a mare into heat earlier in the year.
After a mare has begun to cycle, there are measures that may be used to manipulate the estrus cycle. Prostin is a drug that can be used to interrupt the normal cycle of the mare, and bring her back in heat to allow re-breeding or other procedures during an estrus period. Obviously, the mare must already be cycling for this medication to work.
Regumate is another drug that can be used to manipulate the mare’s estrus cycle. It is also used for mares that require supplemental progesterone to be able to maintain a pregnancy. The schedule for Regumate therapy is complex and is best approached with the help of your veterinarian.