A correlated biochemical and stereological study of periparturient fatty liver in the dairy cow.

Liver lipids were estimated in cows eight weeks before and one and eight weeks after calving by two independent procedures. Liver lipid was estimated stereologically in Araldite-embedded sections and using thin layer chromatography and densitometry of the separated lipids. The results obtained by these methods were compared. There were significant increases in the hepatic content (g/kg liver wet weight) of total lipid, triacylglycerol and non-esterified fatty acids one week after calving, with no significant changes in the phospholipid and cholesterol content around calving. The liver lipid composition (g lipid/100 g total lipid) changed one week after calving, with an increased proprotion of triacylglycerol and a decreased proportion of phospholipids and cholesterol. There was no change in the proportion of non-esterified fatty acids. The volume fracton of the hepatocyte occupied by fat droplets increased one week after calving. There was a high correlation between the triacylglycerol content of the liver determined biochemically and the volume fraction of fat droplets lying within the hepatocyte cytoplasm determined stereologically.