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Journal of Dairy Science Vol. 51 No. 10 1597-1605
© 1968 by American Dairy Science Association ®
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Blood Lipid Changes in Cows of Different Breeds Fed Rations Depressing Milk Fat Test 1

P. N. Varman and L. H. Schultz

Department of Dairy Science, University of Wisconsin, Madison

ABSTRACT

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.

Arteriovenous differences for acetate decreased significantly during the experimental period to almost one-third of the original level, whereas the uptake of triglycerides and ketone bodies was not changed significantly. Levels of blood plasma acetate and triglycerides and blood ketone bodies during the post-experimental period exceeded the original levels and were accompanied by arteriovenous differences exceeding the original levels. The milk fat test recovered to the original level 3 wk after returning to a normal ration. Higher levels of propionate and lower levels of acetate in the rumen during the experimental period appeared to be the key factors responsible for the observed changes.

FOOTNOTES

1 Published with the approval of the Director of the Wisconsin Agricultural Experiment Station.






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Copyright © 1968 by the American Dairy Science Association ®.