| Abstract: | Bone responds to exercise with changes in bone (re‐)modelling, which might be monitored non‐invasively with biochemical bone markers. The aim of this study was to evaluate the influence of exercise on serum osteocalcin and serum carboxy‐terminal cross‐linked telopeptide of type I collagen generated by matrix metalloproteinases (CTX‐MMP) concentration in young racehorses. Seventy‐one 2 to 4‐year‐old Thoroughbreds were included in this prospective infield study. Blood sampling was performed six times (i.e. six sampling cycles) during a 9‐month period. Serum samples were analysed with commercial osteocalcin and CTX‐MMP radioimmunoassays. Two‐year‐old racehorses had higher serum osteocalcin and CTX‐MMP values than 3‐year‐old horses. Gender and training amplitude did not significantly influence serum osteocalcin and CTX‐MMP values. Two‐year‐old horses showed an increase in osteocalcin values between cycles 2 and 3 and an increase in serum CTX‐MMP values between cycles 1 and 2. Serum osteocalcin and CTX‐MMP concentrations decreased between cycles 4 and 5, and 5 and 6. Three‐year‐old horses showed an increase in serum osteocalcin levels between cycles 3 and 4 and an increase in serum CTX‐MMP concentrations between cycles 1 and 2, and 3 and 4. Serum osteocalcin levels decreased between cycles 5 and 6, whereas serum CTX‐MMP levels decreased between cycles 4 and 5, and 5 and 6. Two‐ and three‐year‐old horses showed a decreased osteocalcin/CTX‐MMP ratio between cycles 1 and 2. Moreover, 2‐year‐old horses showed an increase in the osteocalcin/CTX‐MMP ratio between cycles 2 and 3. Sore shin formation did not significantly influence serum osteocalcin and CTX‐MMP values. Serum osteocalcin and CTX‐MMP are promising bone markers for monitoring exercise induced changes in equine bone metabolism. |
