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Evaluation of a hand-held meter to detect subclinical ketosis in dairy cows
TNN is a new hand-held meter for detecting subclinical ketosis of dairy cows by determining blood β-hydroxybutyrate (BHBA). The objective of this study was to evaluate the performance of this new cowside test by comparing BHBA results obtained using the hand-held meter with those results made with a laboratory method and comparing the accuracy between diagnostic performance using blood and using milk and urine. 275 blood samples and 97 urine samples and 85 milk samples from clinically healthy Holstein cows between 1 and 58 days post-calving were analysed. The correlation coefficients for BHBA with TNN versus laboratory methods were 0.92. Based on Bland-Altman plot, agreement between two methods was good for BHBA. In this study, the TNN test had sensitivities of 75 and 88% at 1.2 and 1.4 mmol of BHBA/L of whole blood, respectively. Specificities were 97 and 99%, respectively. Compared with TNN the sensitivities and specificities of urine test and milk test were lower. The sensitivities and specificities were 57 and 80% for milk tests ,respectively, and 71 and 94% for urine tests, respectively, when 1.2mmol/L of blood was defined as the threshold. Raising the threshold of laboratory method to 1.4mmol/L, The sensitivities and specificities were 75 and 79% for milk tests, respectively, and 75 and 93% for urine tests, respectively. We conclude that TNN is a useful tool to diagnose subclinical ketosis and blood tests are better methods than urine tests and milk tests due to higher sensitivity and specificity.
Keywords: subclinical ketosis , β- hydroxybutyrate , diagnostic