Lipid Choroderization of Bovine Serum Lipoproteins Throughout Gestotion and Lactation

Lipid composition of serum lipoproteins was studied in Holstein cows throughout gestation and lactation. Blood serum lipids varied with stage of gestation or lactation; however, the percent lipid distributed in the cholesteryl esters, phospholipids, and unestcrtfied cholesterol did not vary. Cholesteryl esters and phospholipids accounted for approximately 90~ of the lipid content of whole serum. The serum lipoproteins were separated into four ultracentrifugal density classes: very low density lipoproteins and chylomicrons # < 1.006, low density lipoproteins p 1.006 to 1.040, high density lipoproteins sub one p 1.040 to 1.063, and high density lipoproteins p 1.063 to 1.21. The high density lipoproteins, the major class of ]ipoproteins in blood serum, were characterized by cholesteryl esters and phospholipids accounting for about 90% of their lipid content. Triglycerides were not detectable in high density lipoproteins or high density lipoproteins sub one duringlactation. The lipid composition of the high density lipoproteins sub one was similar to that of the high density lipoproteins. The very low density lipoproteins were characterized by triglycerides averaging 59~ of the lipid moiety throughout gestation and lactation. Lipids associated with the very low density lipoproteins varied with stage of gestation and lactation in that during lactation the amount of lipid associated with the very low density lipoproteins was Received December 20, 1972. a Authorized for publication on October 25, 1972, as Paper No. 4320 in the Journal Series of the Pennsylvania Agricultural Experiment Station. 2 Presented at the 1972 Annual Meeting of the American Dairy Science Association, Blacksburg, Virginia. Supported in part by the U. S. Public Health Service, Research Grant HL 03632. 4 Present address: Medical School, University of California -San Diego, La Jolla, California 92037. lower than that during the dry period. The lipid composition of the bovine serum lipoproteins was discussed in relation to gestation and lactation. A role of the very low density lipoproteins in the transport of triglyceride for milk fat synthesis was postulated from their high triglyceride content.