Ketone bodies in milk and blood of dairy cows: relationship between concentrations and utilization for detection of subclinical ketosis.

The objective of this study was to investigate the relationship between the concentrations of the different ketone bodies in milk and blood and to evaluate these concentrations for the detection of subclinical ketosis. A total of 60 multiparous cows were used. Concentrations of acetone, acetoacetate, and beta-hydroxybutyrate were analyzed quantitatively in blood and milk, and the Ketolac strip test was used for semiquantitative determination of beta-hydroxybutyrate in milk. Cows were defined subclinically ketotic when their concentration of blood beta-hydroxybutyrate was over 1200 micromol/L. High correlation coefficients were observed between blood acetone and blood acetoacetate, and between blood and milk acetone. On the contrary, concentrations of milk and blood beta-hydroxybutyrate were poorly correlated with the other concentrations of ketone bodies. The Ketolac strip test overestimated the concentrations of beta-hydroxybutyrate in milk. For the detection of subclinical ketosis, the best sensitivity-specificity combination was obtained with the determination of acetoacetate in blood or milk, with threshold concentrations of 125 and 50 micromol/L, respectively. Determination of beta-hydroxybutyrate in the milk via an enzymatic analysis or via the Ketolac strip test provided valuable results, with threshold concentrations of 70 and 100 micromol/L, respectively. The simplicity of use of the Ketolac strip test makes it a valuable way to investigate subclinical ketosis.