Q: I own a five-year-old mare, and even though she’s special to me, I know she’s not breeding quality. I’ve heard a lot about overbreeding and unwanted horses, and I want to be a responsible owner. Is there any kind of safe and effective birth control method for mares that I could use for her?
Having said this, there are chemical means of mare contraception that are available, although not commercially. The Bureau of Land Management (BLM) has been utilizing long-acting contraceptive vaccines to control herd sizes of feral mustangs for a few years now as part of an effort (in conjunction with increasing adoptions) to reduce the growing numbers of these animals on public land. There does not seem to be a push to have this contraceptive vaccine commercially available, most likely due to the differences in goals of the two equine populations: use in mustangs is strictly for long-term population reduction. The US companion equine industry does not yet seem to require this.
Occasionally, mares develop ovarian tumors that produce high levels of sex steroids that result in the mare acting overly masculine to the point of dangerous aggression. These mares are candidates to have their ovaries removed, thereby sterilizing them in the process.
In summary, the companion horse birth control issue (meaning, excluding feral mustangs) rests mostly on sterilizing the male population through surgical castration. For your mare, the best birth control is abstinence; just keep her away from stallions.
— Anna O’Brien, DVM
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