Early changes in biomarkers of skeletal metabolism and their association to the occurrence of osteochondrosis (OC) in the horse

Reasons for performing study: Diagnosis of osteochondrosis (OC) is based on clinical signs and radiography, but alternative methods for detection at an early stage would be useful. Objectives: To determine in the juvenile horse the relationship between serum concentrations of a number of biomarkers that reflect changes in cartilage and bone turnover and age, feeding level, growth, and the occurrence of OC. Method: Foals were assigned to a high (n = 20) or moderate (n = 19) feeding level group from birth to age 1 year. Bodyweight, withers height and cannon width were measured. Osteoarticular status was assessed radiographically at 5.5 and 11 months in all foals, and by necropsy at 12 months for 8 foals/group. Serum biomarkers of bone (osteocalcin, CTX-1) and cartilage (CPII, C2C) metabolism were assayed at 8 time points between ages 2 and 52 weeks. Ratios between biomarkers of tissue formation and degradation were calculated at each time point. Results: Consistent age-related pattern in biomarker serum concentrates were found, indicating a markedly higher metabolism before age 20 weeks but concentrations were not affected by feeding level. Bodyweight was correlated negatively to C2C and CTX-1, and withers height was positively correlated to osteocalcin and the osteocalcin/CTX-1 and CPII/ C2C ratios. Osteocalcin concentration at 2 weeks and CPII/ C2C ratio at 20 weeks had strong positive correlations to OC, as diagnosed radiographically at 5.5 months. Osteocalcin had a strong correlation with radiographically detected OC at 11 months but at that time there was no significant relationship between CPII/C2C ratio and OC. Conclusions: Occurrence of OC lesions is significantly associated with anabolic changes in bone metabolism during the first weeks post partum, given the strong relation with osteocalcin. Potential relevance: Measuring osteocalcin concentrations during the first few weeks post partum may have potential value for the prediction of risk for OC development.