Comparison of electronic nose and conventional cow-side diagnostic tools for detection of ketosis in early lactation dairy cows

Abstract

Rapid diagnosis of ketosis in dairy cows is imperative for treatment and managing economic losses. Cow-side ketosis diagnostic tools are greatly needed. The objective of this study was to compare three tools for the detection of ketosis, using serum β-hydroxybutyrate (BHB) as the gold standard. The di­agnostic tools tested were: (1) Precision Xtra® handheld blood ketone meter, (2) ReliOn® urine ketone test strip, and (3) Cyra­nose 320® electronic nose (eNose) for use on milk and urine. Dairy cows (n = 60) were sampled immediately post-calving. Whole blood, serum, milk, and urine were collected and ana­lyzed on the same day. Each modality was compared to BHB to determine sensitivity and specificity. Positive predictive value (PPV) and negative predictive value (NPV) were calculated across a range of ketosis, consistent with reported prevalence (10-35%) in U.S. dairy operations. Urine ketone strips provided the highest specificity (99.2%), yet low sensitivity (58.6%). The Precision Xtra demonstrated adequate sensitivity (93.8%) and specificity (92.9%). The eNose had substandard sensitivity and specificity when used on milk (Sn: 58.8%; Sp: 44.3%) and urine (Sn: 18.8%%; Sp: 80.6%) compared to the other modalities. Al­though the actual predictive values change with prevalence, urine ketone test strips had the highest PPV (89.5-97.6%) and Precision Xtra had the highest NPV (99.3-96.5%) across all simulated ketosis prevalences. Both urine ketone test strips and the Precision Xtra are adequate cow-side ketosis detection tools. Further optimization of the eNose is needed before de­ployment as a field diagnostic tool.