Effects of barefoot trimming and shoeing on the joints of the lower forelimb and hoof morphology of mature horses

Twelve mature American Quarter Horses (450-572 kg) were used in a switchback design for a 140-d trial to determine the effects of shoeing on joints of the forelimb and digital cushion depth. The study consisted of 3 phases: d 0 to 42, horses were barefoot trimmed; d 49 to 91, horses were shod (SD) on the forehand with standard St. Croix plain lite shoes; d 98 to 140, horses received another barefoot trim. Horses were exercised 3 times per wk on a linear dirt track. Measurements and blood samples were obtained every 21 d following exercise. Joint circumference was measured using a soft tape measure. Serum was harvested, and prostaglandin E2 was analyzed by ELISA. Digital cushion depth was measured ultrasonically through the superficial frog. Stride lengths were measured at a walk and trot using gait analysis software. Data were analyzed using the MIXED procedure of SAS. Mean stride lengths at the walk (P < 0.05) and trot (P < 0.01) and carpal joint circumference (P < 0.01) were greater in the SD phase than the barefoot phases. There was no effect (P ≥ 0.47) of d or treatment on digital cushion depth; however, on d 42 of each of the phases, mean digital cushion depth was greater (P < 0.01) in the barefoot phases compared with the SD phase. These data indicate that a shod foredigit may cause changes in hoof morphology due to alterations in lower limb movement and hoof load dispersion, which could increase the incidence of lameness over time.