Specificity
was 0.88 or 0.90 using the same cut-points. Repeating
measurements after different time intervals improved
test characteristics only slightly. In the second experiment,
we compared BHBA concentrations of samples
drawn from 3 different blood sampling locations (tail
vessels, jugular vein, and mammary vein) of 116 lactating
dairy cows. Concentrations of BHBA differed in
samples from the 3 sampling locations. Mean BHBA concentration was 0.3 mmol/L lower when measured in
the mammary vein compared with the jugular vein and
0.4 mmol/L lower in the mammary vein compared with
the tail vessels. We conclude that to measure BHBA,
blood samples of continuously fed dairy cows can be
drawn at any time of the day