Science et technologie vétérinaires

The objective of the present study was to emphasize the value of ultrasonography in predicting hepatic fat content in dairy cows during the transition period. For this purpose, five dairy cows during the transition period were examined by ultrasonography 3 times during this phase, 3wk before expected partition (wk -3), at parturition (wk 0) and 3wk after parturition (wk +3). Parallel, blood samples were collected and livers were biopsied. None of the cows showed clinical disease around calving. Compared with precalving values, the hepatic triglyceride and glycogen concentrations were higher at parturition (wk 0) and thereafter (wk +3). Histopathologically, there were no cellular abnormalities in hepatocytes 3 weeks before parturition. However, at parturition the hepatocytes contained some lipid drops in cytosol, and the cells after parturition (wk +3) turn opacificated severely and cellular membranes are indistinct. With increased liver TG content, hepatic ultrasonography showed increased overall echogenicity with vascular blurring. In the field, the visual evaluation of the brightness of hepatic tissue in dairy cows during the transition period can give a rough, but quick estimate of the liver fat content. To the best of the authors’ knowledge, this study is the first that shows hepatic changes by ultrasonography in dairy cows during the transition period.