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Bovine Ketosis and Depressed Fat Test in Milk: A Problem of Methionine Metabolism and Serum Lipoprotein Aberration¹

Department of Dairy Science

L. C. Griel, Jr.

Department of Veterinary Science, The Pennsylvania State University, University Park

ABSTRACT

During early lactation the high producing dairy cow is in a negative energy and protein balance (8, 11). The increased demands for nutrients associated with the initiation of lactation is met by an increased intake of food and also by mobilization of endogenous lipids and proteins from body tissues. We report preliminary findings on the composition of blood lipoproteins during the early weeks of lactation for normal and ketotic cows; postulations on the etiology of the disease; and, the effectiveness of treatment based on these findings. Likewise, the biochemical similarities of bovine ketosis and low fat testing milk will be discussed.

Blood samples from Holstein cows in the University Herd were obtained weekly or more often beginning with the first week of lactation and extending for as long as 16 weeks. All animals were fed the same winter ration of mixed forage with grain supplementation. Cows were clinically examined weekly or more often as needed by the onset of ketosis. ß-lipoproteins were removed from the blood serum by the method of Sakagami and Zilversmit (24). Methods of lipid extraction and fractionation have been reported (18). The animals were classified according to their clinical condition at the time of sampling as normal, subclinical ketotic, and clinical ketotic. A cow was considered to have subclinical ketosis when showing a positive ketouria; and, clinical ketosis when showing ketouria, depressed feed intake, and reduced milk yield.

¹ Authorized for publication as paper no. 3268 in the Journal Series of the Pennsylvania Agricultural Experiment Station.