Do Metal Shoes Contract Heels?-A Retrospective Study on 114 Horses.

Heel contraction is an undesired but common condition in domestic horses. Some authors indicate shoeing as a risk factor. There is a correlation between shoeing and a restriction of heel expansion, but the clinical significance is unknown. This study aimed to evaluate the influence of shoeing and other risk factors, such as age, access to paddock, and breed, on heel contraction. This study included 114 horses, 55 of which were barefoot their whole life and 59 had been shod consistently for at least the previous year. The width and length of the frog were measured. Linear mixed-effects models were performed for the width:length ratio, where the fixed effects were age, sex, breed, pasture or paddock time, shoeing and its duration, and limb. The random effects included the horse and the yard. Although heel contraction occurs more often in shod horses compared with barefoot horses, the difference between the two conditions was not statistically significant, when other factors were considered. The most important factors that impacted contraction were individual horse features and breed (P < .001). The effect of age and a yard was noticed (P < 0,5). The sex, paddock time, and the shoeing and its duration were found not to have statistical significance. The study concluded that heel contraction is multifactorial problem, mainly caused by breed and unknown features correlated with individual. It was not confirmed that horseshoeing causes heel contraction. Because of significant difference in incidence of contraction between yards, there is a need to further investigation of environmental factors causing this hoof distortion.