Prepare your mares for breeding season

Source: Text by Dr. Julie Strachota

Headshot Dr. StrachotaPreparation for the next breeding season often starts before welcoming in the New Year. This begins with putting your mare under lights.

The mare is a seasonally polyestrus animal which means she undergoes regular heat cycles for a portion of the year. The mare will have her first heat cycle with increasing daylight duration in the spring.

We can cause a mare to cycle earlier in the year by increasing the number of hours her retinas are exposed to light. Mares need to be provided 16 hours of continuous light 60-75 days prior to the start of the breeding season.

Daylight provides the necessary amount of light, so turnout is appropriate during the day and stalling at sunset. We recommend that the lighting period be added at the end of the day between 5 p.m. and midnight.

The easiest way to do this is with the use of a timer. If you want your mare to be cycling at the beginning of February, you should begin artificial lighting between Nov. 1 and Dec. 1. The amount of light needed is reported at 10 foot candles of light while stalled (2-8 foot fluorescent bulbs with high output ballasts, at 10 foot height, in a 12×12 stall).

General herd health practices should be completed prior to having the mare bred. The mare should be vaccinated with her core vaccines including Rabies, Eastern Encephalitis, Western Encephalitis, Tetanus and West Nile.

After the first hard frost of the fall, horses should be dewormed with a praziquantel/ivermectin product. It is a good idea to have a fecal checked to make sure a heavy worm burden is not present within the mare’s gastrointestinal tract. Body condition scoring and weight management are also important prior to the breeding season as an obese mare is typically harder to get in foal.

Any routine dentistry is also recommended at this time to insure appropriate mastication and weight.


Julie Strachota graduated from Michigan State University with her Doctorate of Veterinary Medicine and Master’s in Large Animal Clinical Sciences. She began working at Saginaw Valley Equine Clinic two years ago with a focus in equine reproduction. You can email her at or visit her at You can also write to her in care of InStride Edition.

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