Short communication: Validation of a test-day milk test for β-hydroxybutyrate for identifying cows with hyperketonemia

摘要

Subclinical ketosis is a common metabolic disorderaffecting dairy cattle that results in a greater risk forthe development of subsequent metabolic and infectiousdisease. Canwest Dairy Herd Improvement (DHI;Guelph, ON, Canada) has begun to use an infraredtest (MilkoScan FT600, Foss Analytical A/S, Hillerød,Denmark) applied to metered composite milk samplesto detect β-hydroxybutyrate (BHB) levels as a herdsurveillance test for hyperketonemia. However, the testhas not been compared with the gold standard, serumBHB as determined in a reference diagnostic laboratory.The objective of this cross-sectional diagnosticaccuracy study was to validate the DHI milk BHB testto identify cows with hyperketonemia as determined byquantification of BHB in serum. A total of 316 cowsfrom 17 dairy herds in southwestern Ontario had a milkand blood sample taken. Milk was collected at a routineDHI test, and blood from the same cow was sampledwithin 24 h of the milk test. The BHB concentration inmilk was determined using the DHI milk BHB test, andserum was sent to the Animal Health Laboratory at theUniversity of Guelph (Guelph, ON, Canada). A nonparametricreceiver operating characteristic curve wasgenerated to compare DHI milk BHB concentrationswith serum BHB concentrations. Overall, a total of 34cows (11%) had a level of serum BHB ≥1.2 mmol/L.The concentration of DHI milk BHB was moderatelycorrelated with the concentration of serum BHB, yieldinga coefficient of determination value of 0.61. Theoptimal cut point for determining hyperketonemia(≥1.2 mmol/L) on the DHI milk BHB test was ≥0.14mmol/L, yielding a sensitivity of 81% and specificityof 92%. The performance of the DHI milk BHB testvaried depending on the days in milk (DIM) of the cowstested, with a higher specificity being found in cowsthat were ≤25 DIM compared with cows tested >25DIM. If the herd-level prevalence of hyperketonemiawas ≥14%, the DHI milk BHB test had an improvedsensitivity when compared with a herd-level prevalenceof <14%. This study demonstrates that the DHI milkBHB test is a reliable measure for evaluating hyperketonemiausing routine DHI milk samples and could beused as a herd-level monitoring tool for ketosis whenevaluating nutritional management or preventativemedicine strategies.