Lipoprotein metabolism in fatty liver dairy cows.

High yielding dairy cows undergo a period of energy deficit in early lactation and mobilise body reserves for milk production. During this phase lipid infiltration of the liver takes place as a result of fat mobilization and the degree of accumulation of fat in the liver depends on the level of mobilization of fatty acids from the adipose tissue. The objective of the studies reported was to characterize plasma lipoproteins in dairy cows and to determine whether differences in plasma lipoproteins existed in dairy cows with varied degrees of hepatic lipid infiltration. The physiological mechanism responsible for fatty liver is not fully understood but seems to involve a deficit in the hepatic synthesis and release of lipoproteins as shown by the depressed level and compositional modifications of plasma lipoproteins. Other results indicate a negative correlation between plasma apo B concentration and liver triglyceride content. In studies carried out on fatty liver cows the level of liver apo B mRNA was reported to be lower than in control cows. An impaired synthesis of apo B may result in its decreased availability for lipoprotein formation and in turn results in enhanced triglyceride accumulation in the liver.