Monitoring Subclinical Ketosis Using Milk Strip Test and Control Chart in Dairy Herds

Subclinical ketosis (SCK), based on a serum betahydroxybutyrate (BHB) concentration ≥1400 μmol/L (14.4 mg/dL), is a metabolic disease that has been associated with reduced milk production and increased risk of other metabolic disorders. Duffield et al (2001) have reported a median prevalence of SCK of 41% among 25 dairy herds, and a within-herd prevalence ranging between 8 and 80%. A milk strip cow-side test (Keto-Test, Elanco Animal Health, Guelph, Ontario) has been shown to have a sensitivity of 91% and a specificity of 74% to detect SCK in dairy cows when using a cut-off value of 100 μmol/L of BHB (Osborne et al, 2002). Statistical Process Control (SPC) and the use of Control Charts are tools that can be used in order to monitor health status in production medicine programs. Our objectives are to provide an overview of the SPC and Control Charts and to present a practical application of this tool using milk Keto-Test to monitor SCK in dairy herds.