Equine peripheral caries (PC) can cause significant dental pathology and appears to be increasing in prevalence and recognition in many areas [1, 2]. Previous studies have identified risk factors for the condition including the feeding of oaten hay . It was hypothesized that this may be due to the higher water soluble carbohydrate (WSC) or “sugar” content of the hay. A randomized control trial involving 30 horses on three properties was completed. The horses were randomly assigned to two groups: high WSC (H-WSC) or low WSC (L-WSC) oaten hay and were then sedated and intraoral photographs and endoscopy were performed for baseline levels. They were maintained on this assigned hay source for three months when they were again sedated, examined, and photographs and endoscopic videos recorded. Horses with significant PC were then changed to meadow hay (previously shown to be lower risk for PC ) for seven months and re-examined to assess for recovery. Images and videos were anonymized and graded for PC, and the PC grades of the teeth before and after intervention were compared using a Fisher exact test. Thirteen horses fed L-WSC hay and 15 fed H-WSC hay completed the study. Of horses fed the H-WSC oaten hay, 60% deteriorated and of horses on L-WSC oaten hay, 53.8% improved in PC grade over the trial, however, the difference was not statistically significant (P =.274). All three horses available for recheck after changing to meadow hay improved.