Effects of fasting in non-lactating cows. A correlated biochemical and stereological study of fasting-induced fatty liver

Abstract

Summary: Concentrations of serum lipids, concentrations and compositions of liver lipids, and ultrastructural composition of hepatocytes were measured in non-lactating cows following a 6-day fast. There was no change in the concentration of serum lipids due to fasting. The content of total lipid in liver (g/kg of liver wet weight) doubled due to an eightfold increase in triglyceride, a twofold increase in cholesterol ester, a fourfold increase in free fatty acid and a 50% increase in cholesterol. The composition of liver lipids (g lipid/100 g of total lipid) changed with an increase in the proportions of triglyceride and free fatty acid, a decrease in the proportion of phospholipid, and no change in the proportion of cholesterol and cholesterol ester. The ultrastructural composition of the hepatocytes changed in fasted cows with an increase in the volume density of cytoplasm occupied by lipid droplets and lysosomes and a decrease in the volume density of glycogen. The number of mitochondria per cell decreased and volume of individual mitochondria increased. The fatty liver induced by fasting non-lactating cows was chemically and morphologically different from the fatty liver induced by fasting lactating cows.