Effect of age at training initiation on hoof morphology and lameness in juvenile American Quarter Horses

Background Lameness, discipline, training intensity, environmental variability, and shoeing are all factors demonstrated to affect hoof loading and therefore act as adaptive stimuli to alter hoof morphology. Objectives To evaluate the effect of age at training initiation on hoof morphology and lameness incidence and determine if specific hoof morphology measurements correlate with lameness in juvenile American Quarter Horses. Study design Prospective cohort study. Methods American Quarter Horses (n = 42; 29 two‐year‐olds, 13 three‐year‐olds) entering training were monitored for hoof morphology and lameness over 6 months (months 0, 2, 4, and 6). Hoof measurements (palmar/plantar angles, frog base width/length, toe length/angle, heel length/angle, heel and foot width, wall height/angle) from radiographs and photographs were recorded. Lameness was graded subjectively and objectively (Lameness locator®). Statistical analyses were performed with Fisher's exact test and repeated measures ANOVA with p