EFFECTS OF DIETS CONTAINING TALLOW AND SOYBEAN OIL WITH AND WITHOUT CHOLESTEROL ON HEPATIC-METABOLISM OF LIPIDS AND LIPOPROTEINS IN THE PRERUMINANT CALF

The effects of long-chain fatty acids (230 g/kg of dietary DM) from ta llow and from soybean oil, with or without cholesterol (10 g/kg of die tary DM), on hepatic lipid contents and on in vivo hepatic production rates of lipids and lipoproteins were investigated in 22 preruminant m ale calves fitted with chronic catheters and with electromagnetic bloo d flow probes implanted in the hepatic vessels, Diets containing soybe an ail and soybean oil with cholesterol led to the development of trig lyceride infiltration in the liver and to higher apparent hepatic secr etion of very low density lipoproteins than did diets containing tallo w or tallow with cholesterol. Addition of cholesterol to diets favored accumulation of low density lipoproteins in plasma and the net appare nt secretion of these particles by the liver, especially for the diet containing soybean oil with cholesterol. Regardless of the diet, calf liver clearly removed large high density lipoproteins of type 1 that w ere rich in cholesteryl esters but secreted heavy high density lipopro teins that were rich in proteins. The intensity of removal of high den sity lipoproteins of type 1 by the liver depended on the plasma concen tration of these particles, probably by mass action. This removal did not prevent the accumulation of high density lipoproteins of type 1 in plasma, such as it did in calves fed soybean oil.