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Assessment of the accuracy and test characteristics of a multivariable metabolic index to predict hyperketonemia in early postpartum Holstein dairy cows.

L. Caixeta

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06-22-2020

Abstract:

41
Assessment of the accuracy and test characteristics of a multivariable metabolic index to predict hyperketonemia in early postpartum Holstein dairy cows.
Z. Rodriguez1, L. Caixeta*1, P. Ferro1, N. Moraes1, M. Endres1, K. Nakagawa2, A. Imaizumi2, I. Shinzato2, T. Fujieda2. 1University of Minnesota Saint Paul, MN, 2Ajinomoto Co. Inc Kawasaki, Japan.

Hyperketonemia (HYK) is a prevalent metabolic disorder associated with suboptimal health and performance in dairy cattle. Thus, early detection and prevention of HYK are important to improve animal welfare and decrease economic losses. A multivariable metabolic index (MI) using pre-partum concentration of different amino acids and blood metabolites was developed to predict the occurrence of HYK in Holstein dairy cows. Our objective was to assess the accuracy of this MI and the variability of test characteristics at different MI thresholds. Blood samples were collected from Holstein cows in a commercial dairy in Minnesota at 21 � 3 d before expected calving date (3 weeks pre-partum) for the measurement of blood metabolites and calculation of the MI. After calving, blood β-hydroxybutyrate (BHB) was measured at 3 � 1 and 7 � 1 DIM for diagnosis of HYK. Hyperketonemia was defined as BHB >1.2 mmol/L. Cows were enrolled between February and September 2019. Statistical analyses were performed using R software (version 3.4.4). The area under for the receiver operating characteristic curve was calculated as a measure of predictive accuracy. Sensitivity (Se), specificity (Sp), positive predictive values (PPV) and negative predictive values (NPV) at 6 different predictive thresholds were calculated as test characteristics. The prevalence of HYK was 19.0% (95%CI: 15.9 — 22.5). The diagnostic accuracy of the MI to predict HYK was 0.79 (95%CI: 0.73 — 0.85). The best Se and Sp based on Youden's index were 75% and 76%, respectively based on d 7 (Table 1). In conclusion, the MI was able to predict HYK with high accuracy and acceptable Se and Sp up to 3 weeks before the disease onset on the postpartum period.Table 1. Test characteristics1 at different metabolic index (MI) thresholds

MI ThresholdSe (%)Sp (%)PPV (%)NPV (%)
−0.745904092
−1.1*75763195
−1.279702896
−1.588502197
−1.892301696
−2.396101495
1Se = sensitivity; Sp = specificity; PPV = positive predictive value; NPV = negative predictive value.*Represents the MI value with the highest Youden's index.

Keywords: hyperketonemia, prediction, transition period.