Record Medication Use During Equine Gestation

Record Medication Use During Equine Gestation

Because we know very little about medication’s effects on fetal development in horses, keeping a precise medical record of pregnant mares could help contribute to scientific knowledge about fetal malformations.

Photo: iStock

You dream for 11 months about the perfect foal your mare is about to produce—one with a well-conformed body, long legs, and a fuzzy foal coat. But, in the guarantee-free game of horse breeding, remember there’s always a risk for something to go wrong. Fetal malformations, for instance, can occur in horses, but the cause often remains unknown.

A Danish researcher is hoping to get to the bottom of one possible cause: medication use. Because we know very little about medication’s effects on fetal development in horses, keeping a precise medical record of pregnant mares could help contribute to scientific knowledge about fetal malformations, said Jørgen Steen Agerholm, DVM, PhD, DVSci, a professor at the University of Copenhagen Department of Veterinary Clinical Sciences Section for Veterinary Reproduction and Obstetrics.

However, that doesn’t mean breeders should fear using pharmaceutical drugs if their pregnant mares need them. It just means that combined efforts, through good records worldwide, can lead to better understanding when problems do occur. And if they do, informing a specialized researcher can be helpful, Agerholm said.

“Very limited knowledge exists on congenital syndromes in horses,” he said. “And worldwide, there are few experts in congenital syndromes of animals. Most cases are examined by veterinary surgeons or diagnosticians who encounter such cases sporadically and without any specific research interest in the cases.”

A specialist researcher with a research interest in these cases, Agerholm recently investigated a foal aborted at 224 days of gestation. The animal had severe facial abnormalities, including “rudimentary” (only cystlike) eyes, severe facial clefts, and hydrocephalus (an enlargement of the head caused by fluid accumulation within the skull). The mare had previously given birth to a live foal that died shortly after a “red bag” delivery, he said. The mare’s dam had had several live foals and one that died during a difficult birth.

The fetus, aborted at 224 days of gestation, had severe facial abnormalities, including “rudimentary” (only cystlike) eyes, severe facial clefts, and hydrocephalus (an enlargement of the head caused by fluid accumulation within the skull).

Photo: Courtesy Dr. Jørgen Steen Agerholm

While genetics could play a part in the current case of malformation, veterinarians should also consider pharmaceutical drugs’ possible role, Agerholm said. The mare received multiple drugs early in the pregnancy when a second twin embryo was reduced at Day 25 of gestation. Some of the treatment continued until Day 60.

None of the drugs (detomidine, butorphanol, romifidine, butylscopolamine, clenbuterol, flunixin, and altrenogest) the mare received are known teratogens (birth-defect-causing drugs), said Agerholm. However, sometimes compounds can have teratogenic effects during an extremely short window of gestation. For example, cyclopamine, a steroidal alkaloid from the plant Veratrum californicum, causes a disease called cyclopia in sheep that can cause malformations if the dam is exposed to the teratogenic compound on Days 13 or 14 of gestation, but not on Day 15, he said.

Still, that doesn’t mean this mare developed a malformed fetus because of those drugs, Agerholm said. And it doesn’t mean she shouldn’t have been treated with them, because she needed them. But a growing database of medical records could help researchers determine causes in the future.

“Animals, including pregnant animals, should not be treated with pharmaceutical compounds unless there is a clear indication,” said Agerholm. “In this case, the mare was treated because it was necessary. My practical advice is always to record treatments.”

The study, “Bilateral oblique facial clefts, rudimentary eyes and hydrocephalus in an aborted equine foetus,” was published in Reproduction in Domestic Animals

About the Author

Christa Lesté-Lasserre, MA

Christa Lesté-Lasserre is a freelance writer based in France. A native of Dallas, Texas, Lesté-Lasserre grew up riding Quarter Horses, Appaloosas, and Shetland Ponies. She holds a master’s degree in English, specializing in creative writing, from the University of Mississippi in Oxford and earned a bachelor's in journalism and creative writing with a minor in sciences from Baylor University in Waco, Texas. She currently keeps her two Trakehners at home near Paris. Follow Lesté-Lasserre on Twitter @christalestelas.

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