Chemical composition of horse hooves with functional qualities for competing barefoot

Barefoot racing is a common practice within the harness racing industry, but not all horses have hooves of sufficient quality to race sustainably without shoes. There is currently no objective approach available to assess whether a horse's hooves are suitable for barefoot racing, raising animal welfare issues if trainers misjudge the functional qualities of hooves. This study compared chemical composition of the hoof wall and fatty acid (FA) composition of the digital cushion in a group of horses that had raced barefoot often (RB) and a group of horses that could not race barefoot and therefore raced with shoes (RS). Trimmings from the hind hoof wall were collected from the lateral quarters in one sub-cohort postmortem and in another sub-cohort of live horses and analyzed for macro- and microelements, nitrogen, dry matter (DM), and total and free amino acid content. For the postmortem horses, samples of the digital cushion were also collected and analyzed for total and free FAs. RB horses had lower concentrations of copper in the hoof wall (17.5 ± 3.9 vs. 32.8 ± 4.7 mg/kg DM, P = 0.02) than RS horses. RB horses also tended (P < 0.1) to have higher concentrations of nitrogen (164.2 ± 0.2 vs. 163.5 ± 0.3 g/kg DM) and sulfur (22.9 ± 0.2 vs. 22.3 ± 0.3 g/kg DM). RB horses had higher hoof wall concentrations of arginine (10.51 ± 0.05 vs. 10.34 ± 0.06 g/100 g DM, P = 0.03) and showed a trend (P < 0.1) for higher hoof wall concentrations of cysteine (6.14 ± 0.10 vs. 5.82 ± 0.13 g/100 g DM) and proline (4.62 ± 0.05 vs. 4.49 ± 0.06 g/100 g DM). There were no differences between the groups for any other element or amino acid analyzed. There were also no differences between the two groups in terms of FA composition of the digital cushion. These results indicate that chemical composition, especially with respect to copper, arginine, nitrogen, sulfur, cysteine, and proline, may be important for the functional qualities of the hoof capsule and the ability to race barefoot without wearing the hoof down. However, chemical analysis of hoof wall tissue and of the fat content of the digital cushion does not seem to be a definitive method for distinguishing horses that have hooves suitable for barefoot racing from those that do not.