Carry That Weight: Lameness in Pregnant Mares

Lameness is not an uncommon condition in pregnant mares. But does pregnancy itself make a horse more prone to lameness?

"Any horse can become lame while pregnant, but pregnancy does not make lameness more likely as a single factor," said Sarah Sampson, DVM, a WSU clinical instructor of equine surgery and orthopedic sports medicine. "They can step on a nail, cut themselves, or become injured in the pasture just like any other horse. But a lot of mares become brood mares because they were performance animals that became injured and were retired. Often these horses may have preexisting conditions before being bred like osteoarthritis, navicular syndrome, tendonitis, or suspensory ligament injuries."

Such problems can become aggravated as the mare gains weight throughout her pregnancy--usually up to 200 pounds of extra weight at term from the foal, placenta, and gestational fluids.

"The weight gain mares experience through pregnancy makes it harder on their joints, tendons, and ligaments, and it can become harder for owners to manage any preexisting condition," Sampson said. "A lot of times, brood mares don't have the same management during pregnancy; for instance, some owners may decide to stop shoeing their mare while she is pregnant. Some mares with preexisting lameness issues may need to be kept in shoes and their medication continued, although medication changes may need to be made during pregnancy."

It is always best to have a breeding soundness evaluation done before mares are bred regardless of their past medical history. This should include a reproductive tract examination to make sure she is healthy enough to sustain a pregnancy and a physical and lameness examination to make sure the mare is in good shape systemically and orthopedically. A veterinarian can recommend a management plan and proper medication if needed.

If a mare is not sound enough to carry a foal throughout pregnancy, embryo transfer can be an option for some breeds.

Embryo transfer is a procedure in which the fertilized egg of the desired mare is implanted in another healthy mare's uterus to carry to term. This can also be an option for owners who would like a foal, but also want to keep their mares in competition.

"There is no reason to keep a pregnant mare from competition or pleasure riding in the first half of pregnancy if she is used to those activities and is healthy," Sampson said. "If they are ridden late in their pregnancy, they may become more prone to injury due to the increased weight, and the work will become harder for them physically. If a mare was inactive before being bred, pregnancy is not the time to start training."

Breeding soundness evaluations and embryo transfers are offered through Washington State University's theriogenology service at the Veterinary Teaching Hospital and lameness evaluations are offered through the equine surgery service. For more information or to make an appointment, contact the hospital at 509/335-0711 or the theriogenology service at 509/335-0741.

Reprinted from the WSU College of Veterinary Medicine Equine News Winter 2009 issue.

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