Blood concentrations of beta hydroxybutyrate in clinically normal Holstein-Friesian herds and in those with a high prevalence of clinical ketosis.

: Statistical parameters necessary for the comparison of herd blood beta hydroxybutyrate (HB) concentration means with HB concentrations in the general population were determined in 11 clinically normal herds of Holstein-Friesian cows. These parameters were then used to compare clinically normal cows from 2 Holstein-Friesian herds experiencing a high prevalence of clinical ketosis with the normal population. Blood HB concentration means were compared with plasma glucose concentration means for their relative value as predictors of clinical ketosis prevalence within a herd. Blood HB concentration values were distributed approximately log normal and were directly related to amount of milk production. Herds with a high prevalence of clinical ketosis had blood HB log means higher (P less than 0.01) and glucose means lower (P less than 0.05) than did the normal population. Herd blood HB log means should be determined on 7 or more animals within specified production groups. When these means exceed the normal population log mean by more than 1 SD, susceptible cows in the herd may be at increased risk for the development of clinical ketosis. Blood HB log means may be of greater value than are plasma glucose concentration means for the prediction of herd ketosis prevalence.