Changes in hoof morphology in racing Thoroughbreds during a period of ninety days unshod

Low hoof angles and discrepancies in the dorsal heel are linked to musculoskeletal breakdown, suspensory apparatus failure, and retirement in Thoroughbred racehorses. Evidence-based research on correcting hoof adaptations is limited, which leads to a reliance on therapeutic shoeing.

This study aimed to test the hypothesis that morphological changes occur during active unshod training and that trimming immediately affects hoof angles.

This is a controlled, quantitative, longitudinal study that uses a convenience sample.

A total of 36 racehorses were divided into an unshod treatment group (n = 23) and a control group (n = 13) that remained shod between hoof-care cycles. Trimming followed a recognised standard. Photogrammetry was used to compare initial, endpoint, pre-, and post-trim lateral and solear images.

Trimming improved the dorsal hoof wall angle (DHWA), heel angle (HA), and the DHWA-HA difference (p = 0.001) and altered solear morphometrics (p = 0.001, treatment; p = 0.003, control). Quantified longitudinal, pre-trim treatment data at the end of the 90-day study revealed that the DHWA remained stable (51.22 ± 3.28° to 51.31 ± 3.03°), while the HA increased (29.97 ± 8.81° to 34.62 ± 7.77°) (p = 0.005), and the DHWA-HA difference decreased (21.25 ± 6.90° to 16.69 ± 6.44°) (p = 0.001). Control group results were non-significant. A moderate negative correlation between the DHWA and age (r = -0.412, p = 0.001) indicated that the DHWA decreased as the horses aged.

The study utilised a convenience cohort of racehorses; a larger control group was preferred.

A 90-day period of unshod training restores hoof morphology, offering non-invasive solutions to mitigate hoof-angle-related injury, early retirement, and financial loss. Increased HA and a decreased DHWA-HA difference suggests that the stimulation of the frog, digital cushion (DC), and neuroreceptors drives hoof remodelling. Farriers are often pressured to manipulate the DHWA through trimming the dorsum, this study provides evidence that heel angle, and palmar hoof function should be prioritised. Immediate post-trim improvements imply that greater deterioration occurred during the hoof-care cycle in the control group, indicating that shorter cycles may be necessary for optimal hoof morphology. The findings show that age-related reduction in the DHWA persists for longer than has previously been reported.