Hoof unevenness in juvenile Quarter Horses during first six months of training.

The role of hoof morphology is increasingly recognized as a factor associated with lameness incidence in performance horses. The primary objective was to evaluate effect of training initiation on hoof unevenness in Quarter Horses (n=42; 29 2-year-olds, 13 3-year-olds) over 6-months (m) in training (m0,m2,m4,m6). Horses were objectively assessed for lameness (inertial sensor system) and photographs and radiographs of feet were taken.  Hoof measurements were taken (palmar/plantar angles, frog base width/length, toe length/angle, heel length/angle, heel/foot width, wall height/angle), and analyzed with regards to laterality. Front and hindfoot pairs were determined even if toe angles were within 1.5°. Statistical analyses were performed (Fisher's exact test, mixed-model linear regression, P<0.05). There were no differences in distal phalanx palmar/plantar angle between lame/non-lame forelimbs (p=0.54) or hindlimbs (p=0.20). Unevenness between front feet was seen in toe angle m6 (p<0.001), heel length m6 (p=0.01) and heel angle over time (p=0.006). Unevenness between hind feet was seen at m6 in toe angle (p<0.001), heel length (p=0.009) and heel angle (p=0.02). Lameness incidence did not differ between even and uneven footed horses in forelimbs (p=0.64) or hindlimbs (p=0.09). In uneven feet, there was no difference in lameness between high versus low foot in forelimbs (p=0.34) or hindlimbs (p=0.29). Limitations include lack of control group not entering training, lack of consistency in timing data collection to previous trimming, and small sample size. In summary, differences in foot measurements and laterality were noted over time following training initiation in juvenile Western performance horses.