Influence of type and breed of horse on serum osteocalcin concentration, and evaluation of the applicability of a bovine radioimmunoassay and a human immunoradiometric assay [corrected].

OBJECTIVES

To evaluate applicability of a human osteocalcin (OC) immunoradiometric assay (IRMA) for use with equine serum and compare it with a bovine radioimmunoassay (RIA) previously proven valid for such samples, and to describe the effect of type and breed of horses on serum OC concentration.

ANIMALS

100 healthy horses of either sex, classified as type I or II (draught or warmblood, respectively). Each type was represented by 2 breed groups, each comprising 25 horses.

PROCEDURE

Blood samples were collected in the morning, and the serum was separated. Osteocalcin was measured, using commercially available RIA and IRMA kits, according to the manufacturer's instructions. All samples were evaluated in duplicate.

RESULTS

The human IRMA did not recognize equine OC. Significant variations in the bovine RIA results were observed between types of horses. Draught horses had lower OC concentration, compared with warmblood horses. Significant difference was not observed between breeds for type of horse. Sex had no influence on serum OC values, but age was a significant covariable for both types of horses.

CONCLUSIONS

No crossreactivity exists between the equine and human amino- and/or carboxy-terminus of OC, using this particular human IRMA kit. Difference in blood OC concentration exists between draught and warmblood types of horses.

CLINICAL RELEVANCE

Use of this human IRMA kit is not valid for equine serum. Horse type must be taken into account when evaluating OC concentration in research or clinical situations, especially if small variations in OC concentration are expected.