Biochemical changes associated with the fatty liver syndrome in cows

There were significant changes in enzyme activities and concentrations of metabolites in the blood and liver of cows with fatty livers when compared to normal cows. Blood and liver samples were taken from cows at the abattoir immediately after slaughter. The liver was checked for pathological signs and the samples were divided according to the degree of fatty changes. Three groups were studied: controls showing no gross pathological signs, mild fatty infiltration and severe infiltration. In cows with fatty liver, there were significant increases in the serum activities of isocitric dehydrogenase (ICDH), glucose-6-phosphate dehydrogenase (G6PDH), glutamic dehydrogenase (GLDH), lactic dehydrogenase (LDH), malic dehydrogenase (MDH), aspartate aminotransferase (AST), alkaline phosphatase (ALP) and acid phosphatase (ACP). In the fatty liver, the activities of the enzymes, ICDH, G6PDH, LDH, MDH, ALP and malic enzyme (ME) were significantly higher, while sorbitol dehydrogenase (SDH) was significantly lower. While serum total lipid decreased, the opposite was seen in the liver with higher lipid content, mainly due to triglycerides and cholesterol esters. The significant increases in the NADPH generating enzymes ME, ICDH, G6PDH and MDH, which are required for fatty acid synthesis, suggest that the lipids accumulated in the liver are not only of extrahepatic origin, mobilized into the liver, but also arise from increased lipid synthesis in the liver which is induced during the laying down of fat in the liver. Measurement of the serum NADPH generating enzymes may serve as a useful biochemical test specific for fatty liver in cows.