Abstract
In a riding stable keeping about one hundred horses, a high incidence of white line disease (WLD) related to diet variations was examined from 1992 through 1997. During the first year, the jumping horses (group A) and the dressage horses (group B) were fed mainly with alfalfa hay cubes, timothy hay, barley, salt and calcium supplements. In contrast, the school horses (group C) were fed with Yuusyun® (YS), a pelleted feed, instead of barley, and no salt or calcium supplement. WLD was then detected only in groups A and B. Since the second year, the diets for groups A and B have been changed to supply YS, and after the third year the incidence of WLD decreased significantly. The typical diet fed to groups A and B before the change (P-diet) was short of zinc and copper, and the improved diet (N-diet) provided enough zinc and copper. The other nutrients contained in either diet were enough. It is therefore inferred that the high incidence of WLD which appeared in this stable was caused by feeding low-zinc and low-copper diets to adult performance horses for a long time.
