Decreases of Apolipoprotein B-100 and A-I Concentrations and Induction of Haptoglobin and Serum Amyloid A in Nonfed Calves.

Reduced feed intake near parturition is suggested to be one of the major causal factors for the development of fatty liver in cows, and nonfeeding has been used as an experimental model for fatty liver. In cows with fatty liver, concentrations of lipoprotein lipids and proteins are decreased. In addition, the acute-phase protein haptoglobin is induced. The purpose of the present study was to examine whether the decrease of lipoprotein concentrations and the induction of acute-phase proteins were similarly reproduced by non-feeding. Holstein female calves (n=5) were nonfed for 3 days and thereafter refed. Serum concentrations of nonesterified fatty acids and beta-hydroxybutyric acid were initially increased by the nonfeeding, and followed by decreases in concentrations of cholesteryl esters, phospholipids, apolipoprotein (apo) B-100 and apoA-I. The apoC-III concentration was not distinctly decreased. Haptoglobin and serum amyloid A were induced during the nonfeeding and refeeding process. Haptoglobin was distributed in different proportions in the high-density lipoprotein, very high-density lipoprotein and the lipoprotein-deficient fractions, whereas almost all serum amyloid A was associated with the high-density lipoprotein fraction. These results suggest that the decreases in lipoprotein concentrations and induction of acute-phase proteins found in cows with fatty liver and those with fatty liver-related diseases such as ketosis are primarily due to the reduced feed intake near parturition.