Routine testing for milk beta-hydroxybutyrate for the detection of subclinical ketosis in dairy cows

The milk beta-hydroxybutyrate (BHB; 3-hydroxybutyric acid) concentrations were determined semi-quantitatively by means of Ketolac BHBR in 284 Israeli-Holstein cows (3 herds) on day 5, 6 or 7 post partum. The prevalence of ketolactia indicating subclinical or clinical ketosis differed markedly between herds as did the incidence in cows calving in summer or in autumn. Cows with milk BHB concentrations in the range ?100 to 199 æmol/litre, in particular those with ?200 æmol/litre were at markedly higher risk to develop clinical ketosis during early lactation than cows having a lower milk BHB content at the time of testing. Relationships between increased milk BHB concentrations at the time of testing and the incidence of genital disorders as well as to impaired reproduction in the following period could be shown. Milk testing for BHB therefore, although performed only at the end of the first week post partum, conveyed valuable information. It seems that routine testing for ketolactia is particularly important in cows under heat stress.