Changes in serum B hydroxybutyrate concentrations in dairy cows kept under commercial farm conditions.

beta hydroxybutyrate (BHB) serum concentrations were measured at regular intervals throughout a lactation in groups of animals from three commercial dairy herds. The period of study covered all the major seasonal management changes. BHB levels changed significantly only when the dietary intake of the cows was altered either in quantity of quality. The changes in concentrations of serum BHB were of particular interest during the two grazing seasons when the deteriorating quality of the pasture was reflected in significantly higher concentrations. It is considered that serum BHB concentrations are worthy of further investigation as a parameter for inclusion in preventive medicine monitoring schemes for commercial dairy herds.