CYCLIC FLUCTUATIONS IN ACETONE CONCENTRATIONS IN THE BLOOD AND MILK OF CLINICALLY HEALTHY DAIRY-COWS

Milk samples were taken daily or twice weekly, and blood samples twice weekly, from six clinically healthy dairy cows. Acetone concentration was determined by a new headspace gas-chromatographic method that pro ved to be suitable in terms of practicality, sensitivity and precision . The concentration of acetone in milk was closely correlated with tha t in blood (r2 = 0,967). There was no relationship between lacteal ace tone concentration and either somatic cell count or bacterial infectio n. In both blood and milk there were fluctuations in acetone concentra tion that were synchronous between the six cows. The fluctuations were apparently cyclic, with a period of approximately 10 d. Such fluctuat ions have not previously been reported.