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

Equine Vet J. 2022 Dec 26. doi: 10.1111/evj.13913. Online ahead of print.


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 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 2-year-olds, 13 3-year-olds) entering training were monitored for hoof morphology and lameness over six months (months 0,2,4,6). 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 < 0.05.

RESULTS: 25/42 horses developed sub-clinical lameness (16/42 forelimb, 19/42 hindlimb), with three-year-olds developing lameness more frequently compared to two-year-olds overall (p=0.04; 84.6 vs. 48.3%) and in forelimbs (p=0.05; 61.5% vs. 27.6%); no difference was noted between two- versus three-year-olds in hindlimbs (p=0.2; 61.5% vs. 37.9%). In lame versus sound forelimbs, three-year-olds had decreased foot width (p=0.03; 11.48cm (CI 10.68-12.28) vs. 12.21cm (CI 11.99-12.42)), decreased toe length (p=0.03; 6.02cm (CI 5.69-6.36) vs. 6.45cm (CI 6.32-6.58)), shorter lateral wall height (p=0.03; 4.64cm (CI 4.31-4.96) vs. 5.11cm (CI 5.03-5.2)), and shorter medial wall height (p=0.02; 4.58cm (CI 4.06-5.10) vs. 5.15cm (CI 4.99-5.30)). In lame versus sound hindlimbs, horses overall (p = 0.05; 3.74, CI 3.53-3.96 vs 3.55, CI 3.48-3.61) and three-year-olds had longer heels p=0.01; 3.90cm (CI 3.5-4.3) vs. 3.50cm (CI 3.39-3.61)).

MAIN LIMITATIONS: Small sample size, lack of control group not entering training.

CONCLUSIONS: Three-year-old American Quarter Horses entering training were more likely to develop forelimb lameness than two-year-olds. This sub-clinical lameness was associated with specific hoof morphology characteristics (decreased foot width, toe length, heel length, and lateral/medial wall height; greater toe angle). This article is protected by copyright. All rights reserved.

PMID:36572927 | DOI:10.1111/evj.13913

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