Mean BHBAconcentration 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. A single measurement
provides very good test characteristics for on-farm con-
ditions. Blood samples for BHBA measurement should
be drawn from the jugular vein or tail vessels; the mam-
mary vein should not be used for this purpose.
Key words: subclinical ketosis, β-hydroxybutyric
acid, diurnal rhythm, herd health