Blood Lipid Changes in Cows of Different Breeds Fed Rations Depressing Milk Fat Test

Blood lipid changes in response to a high-grain ration that depressed milk fat test were studied in four cows each of the Guernsey, Holstein, and Jersey breeds. Milk fat percentage decreased from 4.9 to 3.7 in Guernseys, 3.3 to 2.2 in Holsteins, and 5.3 to 4.3 in Jerseys. Protein content of the milk increased. Although there were some significant breed differences in levels of the blood lipid components, within-breed variations were considerable. Plasma levels of phospholipids, cholesterol esters, free cholesterol, free fatty acids, and acetate decreased during the experimental period in all the breeds. Over-all mean arteriovenous differences exceeded 10% of the arterial level only in acetate, triglycerides, and ketone bodies.