Your Guide to Equine Health Care

Deworming Broodmares Near Foaling

A reader’s mare is due to foal in March. Should the mare be dewormed again before she foals? An equine reproduction specialist responds.

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deworming broodmares near foaling
A dose of ivermectin for mares on the day of foaling can help prevent threadworm-associated diarrhea in foals. | Photo: iStock

Q.I have a mare due to foal March 15. I dewormed her Jan. 9 with ivermectin. Should I deworm her again before she foals, and, if so, with which product?

—Via e-mail

A.I typically would not recommend deworming your mare again until she foals. The day a mare foals, we administer the dewormer ivermectin. This is to stop the streak of the parasite Strongiloides westeri (threadworms), which actually travels from the mare into the mammary gland and through the milk into the foal. A dose of ivermectin on the day of foaling will kill any parasites remaining and this will help prevent this parasite as a cause of early foal


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Written by:

Ryan Ferris, DVM, MS, Dipl. ACT, owns Summit Equine in Newberg, Oregon, with his wife, Dr. Dora Ferris. The practice specializes in equine reproduction and sports medicine. He graduated from veterinary school at Washington State University in 2007 and then completed an internship in equine surgery, medicine and reproduction at the Equine Medical Center of Ocala in 2008. He subsequently completed a two-year equine theriogenology residency program at Colorado State University (CSU) and worked at its Equine Reproduction Laboratory from several years.

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