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 proved to be suitable in terms of practically, sensitivity and precision. The concentration of acetone in milk was closely correlated with that in blood (r2 = 0.967). There was no relationship between lacteal acetone concentration and either somatic cell count or bacterial infection. In both blood and milk there were fluctuations in acetone concentration that were synchronous between the six cows. The fluctuations were apparently cyclic, with a period of approximately 10 d. Such fluctuations have not previously been reported.