Fasting and refeeding in the lactating dairy cow: 2. The recovery of liver cell structure and function following a six-day fast

Abstract

Cows in early lactation were fasted for 6 days and then refed a normal diet for 70 days. Liver cell structure was monitored throughout the experiment by stereological analysis of needle biopsy samples and liver cell function was assessed by the activities of aspartate aminotransferase, sorbitol dehydrogenase and concentrations of bilirubin in the serum. The main changes in the liver of the fasted cows were a decrease in volume density of cytoplasm occupied by glycogen, and an increase in volume density of lysosomes and lipid, both lipid droplets and liposomes. There was a decrease in the number of mitochondria per cell with an increase in mean mitochondrial volume. The changes in liver structure were accompanied by a rise in serum enzyme activity and in the concentration of bilirubin in serum. Liver cell volume and volume density of cytoplasm occupied by glycogen, lysosomes and liposomes returned to control levels within 8 days after refeeding whereas volume density of lipid droplets and the mitochondrial parameters returned to control levels within 16 days. During refeeding there was a close correlation between recovery of liver cell function assessed by blood enzyme concentrations and liver cell structure assessed by stereological techniques.