[Plasma lipoproteins of the preruminant calf]

The main lipoprotein classes (HDL, LDL, VLDL, chylomicrons) were isolated from the plasma of four 3-week old preruminant Friesian calves. The proportions of proteins and lipids and the fatty acid composition of the different lipid classes were determined over a 7-hour period corresponding to the pre and post-prandial periods. HDL, LDL, VLDL and chylomicrons averaged 58.3, 19.0, 13.3 and 9.1%, respectively, of total lipoproteins. Triglycerides predominated in VLDL and chylomicrons, and cholesterol esters and phospholipids in HDL and LDL. The lipid proportion and fatty acid composition of a given lipoprotein were stable, except for the triglycerides of the chylomicrons (and VLDL) which were hydrolysed during a 2 to 5-hour period after the morning meal, leading to a higher saturation of the remaining triglycerides. Linoleic acid, abundant in cholesterol esters of HDL (46.5%) and LDL (37.2%) and scarce in the cholesterol esters of VLDL (3.5%) and chylomicrons (3.2%), underlined the dual origin (plasma and tissues) of cholesterol esters in young bovines.