Congenital Flexural Limb Deformities in Foals

University of Kentucky researchers examine the genetics of congenital flexural limb deformities in foals.

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A new foal’s arrival is an exciting time. After 11 months of gestation and caring for the mare and watching her belly expand, delivering a healthy foal is one of the best experiences for a horse owner. Sometimes, however, foals are born with flexural limb deformities (FLD). Many of these foals present with severe FLD called contracted foal syndrome (CFS), which in its worst form involves all four limbs, the neck (torticollis), skull (wry nose), and spine (scoliosis). One third of these foals will be euthanized. However, other less severely affected foals with only one or two affected limbs involved might recover with surgery, splinting, and therapy.

The availability of the horse genome sequence and the subsequent development of genomic tools have facilitated a study of FLD/CFS led by Teri Lear, PhD, associate professor in the genetics/genomics group at the University of Kentucky (UK) Gluck Equine Research Center. Collaborators on the study include Ernie Bailey, PhD, professor in the genetics/genomics group at the Gluck Center; Uneeda Bryant, DVM, assistant professor in pathology at UK’s Veterinary Diagnostic Laboratory (UKVDL); Craig Carter, DVM, PhD, Dipl. ACVPM, director of the UKVDL; Steve Reed, DVM, Dipl. ACT, Rood & Riddle Equine Hospital; and Luigi Auletta, a visiting veterinarian from Italy working at Rood & Riddle.

"We have collected DNA samples from affected foals for a pilot study," Lear said. "All of the foals had all four limbs affected and most had scoliosis, wry nose, and torticollis. Our preliminary results highlighted three regions on three different chromosomes indicating the condition is complex and may involve multiple genes. Genomic testing is expensive, and we still need to test many more horses to hone in on the candidate genes that might cause FLD/CFS."

This condition has been reported primarily in Thoroughbreds but also occurs in Standardbreds, American Saddlebreds, Quarter Horses, and other breeds. Males appear to be more commonly affected, and multiple affected limbs occur more often than a single affected limb. To make matters worse, foals with FLD/CFS can be a serious risk to mares during birth. Up to 16% of dystocia (difficult birth) cases might be due to FLD/CFS affected foals. This might require the mare to undergo a Caesarian, or C-section, increasing her risk of death

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