Evaluation of the influences of exercise, birth date, and osteochondrosis on plasma bone marker concentrations in Hanoverian Warmblood foals.

Objective-To determine whether plasma concentrations of bone turnover markers in growing Hanoverian foals are influenced by age, housing conditions, or osteochondrosis. Animals-165 healthy foals and 119 foals with osteochondrosis. Procedures-Foals were allocated according to birth date and housing management into groups of early-born (born before March 31, 2001; n = 154 foals, 88 of which were healthy and 66 of which had osteochondrosis) and late-born (born after March 31, 2001; 130 foals, 77 of which were healthy and 53 of which had osteochondrosis) foals. Plasma osteocalcin and carboxyterminal propeptide of type I collagen concentrations were analyzed as markers of bone formation, and carboxyterminal telopeptide of type I collagen concentration was analyzed as a marker of bone resorption. Foals underwent radiographic evaluation to screen for osteochondrosis. Results-Plasma concentrations of osteocalcin, carboxyterminal propeptide of type I collagen, and carboxyterminal telopeptide of type I collagen decreased with age, but these changes were more distinct in late-born foals than in early-born foals. Neither sex nor predisposition to develop osteochondrosis affected the pattern of bone marker changes in either group. Conclusions and Clinical Relevance-An age-related decrease in concentrations of bone markers was seen during the first 200 days of life. Changes in bone marker concentrations were similar for foals with osteochondrosis and healthy foals. The correlation between the decrease in bone marker concentration and date of birth indicates that there are differences in skeletal development between early- and late-born foals.