ADVERTISEMENT New research has revealed the Warmblood fragile foal syndrome (WFFS) allele in 21 breeds. The study, an international collaboration led by UC Davis Veterinary Genetics Laboratory Director Rebecca Bellone, PhD, screened more than 4,000 horses from 38 horse breeds in the United States and Europe. Affected breeds were mainly Warmbloods, with the highest carrier frequencies (17%) observed in Hanoverians and Danish Warmbloods. Researchers did not detect the allele in two Warmblood breeds, the Swedish Warmblood and Zangersheide Warmblood, but sample sizes for both breeds in this study were small (16 and 10, respectively). The average WFFS carrier frequency across all Warmbloods tested was 11%. Non-Warmblood breeds included Haflinger, American Sport Pony, and Knabstrupper. The WFFS allele had previously been reported at a low frequency in Thoroughbreds (2.4% carrier frequency in 716 Thoroughbreds tested).