The objective of this study was to determine optimal thresholds of serum concentrations of metabolites that were associated with an increased risk of hepatic lipidosis. Serum and liver specimens of 506 Holstein dairy cows were taken immediately after slaughter. Before slaughter, blood specimens were collected from the coccygeal vein. Serum concentrations of total bilirubin, cholesterol, triglyceride, BHBA, NEFA and activity of AST was determined and the ratio of NEFA to cholesterol was calculated. Total lipid content of liver was also measured. Metabolite concentrations in serum were considered as predictors of hepatic lipidosis in a logistic regression statistical model. The model also included BCS, parity, and cause of culling and stage of lactation as covariates. ROC analysis was used to determine the critical thresholds for predicting hepatic lipidosis. Cows with hepatic lipidosis had significantly higher concentrations of BHBA, NEFA, bilirubin, activity of AST, and NEFA to cholesterol ratio but had lower concentrations of cholesterol in comparison with cows without fatty liver. Serum NEFA >0.566 mmol/L (Odds Ratio (OR) = 5.7; 95% CI = 3.1 to 10.4), BHBA >780 μmol/L (OR = 13.6; 95% CI = 5.9 to 28.9), NEFA/cholesterol ratio >0.2 (OR = 9.9; 95% CI = 5.4-18.3) and AST >120 U/L (OR = 2.9; 95% CI = 1.5 to 5.3), were associated with risk of hepatic lipidosis. The results showed that the best predictor of hepatic lipidosis was BHBA due to highest odds ratio and likelihood ratio positive. However, the ratio of NEFA to cholesterol was a very accurate test to predict hepatic lipidosis due to highest area under curve (77%).

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