Vet Q&A For Pregnant Mares

When it comes to looking after the health protocol for +40 horses, some things are fairly straightforward. Deworming, vaccinations, dental and hoof care are all regular considerations we schedule, organize and then record to ensure our herd is at the peak of its health. However, when it comes to these same aspects regarding our broodmares (or mares that we have gotten in foal for the upcoming year), we often think twice. Some regular health protocols all of a sudden aren’t so regular if a mare is partway through gestation and may need to be held off in between pregnancies. Or it may be that different protocols might come into place altogether concerning broodmares.

Dr. Chris Berezowski DVM, DACT, DABVP (Equine) of Moore Equine Veterinary Centre in Calgary, AB, has kindly offered to help answer some of these common broodmare concerns.


Q. Deworming in broodmares is something that has me really concerned – Can you please outline a proper deworming schedule for broodmares year-round?

A. Deworming protocols always seems to be a scary topic for most people. It is true that Ivermectin is the most commonly recommended safe dewormer. Other options for dewormers that have been proven safe for pregnant mares include fenbendazole and moxidectin. Quest Plus and Eqvalan Gold are not approved for use in pregnant mares.

My general recommendation for deworming pregnant mares is to use a rotation of ivermection, moxidectin and fenbendazole during pregnancy and then a Quest Plus after foaling but before rebreeding.

Q. Do you need to keep lights on in your foaling barn, after the foal is born, if you are planning to breed your mare on her foal heat? And do lights help a mare cycle any better if she is already pregnant?

A. Yes, if a mare foals early in the season (Jan – April) but is not under artificial light, she will most likely not be having fertile heat cycles until late April or May.  Even though she was pregnant, she still needs the artificial lighting to stimulate her to cycle early.

Artificial lighting won't help a mare cycle better if she is already pregnant.  The benefit of artificial lighting is to have an earlier start to the breeding season.


Q. Would you do a pregnant mare's teeth? Is anesthetic ok for them?

A.  I prefer not to sedate any mare during pregnancy unless it is absolutely necessary. The reason is that the sedation given to the mare also makes its way to the fetus.  Situations where the mare has a medical issue that necessitates sedation (colic, laceration, etc…) is when I would use it, as the benefit outweighs the risk. For things like a yearly dental, I would wait until the mare is not pregnant. This is a good thing to do prior to rebreeding next spring.

Q. I understand that Ventipulmin may not be safe for mares in late gestation? If so, why not?

A.  It is true that Ventipulmin is not safe to use in late gestation mares. The reason is that it can interfere with the activity of oxytocin and the normal contraction of the uterus during labor.


Q. If you had a mare that gave birth to a foal that did not receive enough colostrum from her this year, would you breed her again? Would embryo transfer be a safer bet?

A. If a mare has produced either a low amount or low quality colostrum on a previous foaling, there is a significant chance that it will happen again on a subsequent foaling.  In these situations, you can use high quality colostrum from another mare and feed it to the newborn foal or you can administer IV plamsa to the foal.  Embryo transfer is an option but there is no guarantee that the recipient mare will produce adequate colostrum either.

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