Evaluation of the use of nonesterified fatty acids and β-hydroxybutyrate concentrations in pooled serum samples for herd-based detection of subclinical ketosis in dairy cows during the first week after parturition

Objective-To evaluate the use of nonesterified fatty acids (NEFA) and beta-hydroxybutyrate (BHBA) concentrations in pooled serum samples for herd-based detection of subclinical ketosis (SCK) in dairy cows after calving. Design-Cross-sectional study. Animals-1,100 dairy cows from 110 herds. Procedures-Blood samples were collected from 10 healthy cows/herd in the first week after parturition. Aliquots of serum were mixed to create a pooled sample. Concentrations of NEFA and BHBA were measured to estimate prevalence of SCK. Pooled sample test results were compared with those obtained for individual samples. Linear regression and receiver-operating characteristic curve analysis were performed; Bland-Altman plots were used to evaluate agreement between methods. Results-Overall prevalence of SCK was 30.7%, 19.3%, and 13.6%, as determined by use of BHBA threshold concentrations of 1,000, 1200, and 1,400 mu mol/L, respectively. Pooled sample concentrations of NEFA and BHBA were significantly correlated (r = 0.98 and 0.97, respectively) with individual sample means and with the number of cows that had NEFA (R-2 range, 0.81 to 0.84) or BHBA (R-2 range, 0.65 to 0.76) concentrations above predefined thresholds. Pooled sample concentrations of NEFA and BHBA were very accurate to highly accurate for herd-based detection of SCK. Conclusions and Clinical Relevance-Analysis of NEFA and BHBA concentrations in pooled serum samples was useful for herd-based detection of SCK. A sample size of 10 cows/herd was deemed adequate for monitoring dairy herds for SCK. Reference criteria specific to pooled samples should be used for this type of herd-based testing. (J Am Vet Med Assoc 2012;240:1003-1011)