In this KFPS College Tour, Dr Bart Ducro, researcher from Wageningen UR, explains the current state of research into hereditary defects in Friesian horses. He explains how hydrocephalus and dwarf gene carriers were discovered, how to take this into account in breeding, and he provides an update on the collaboration with the American Fenway Foundation and the University of Kentucky to find the genetic origin of esophageal dilatation.