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Alterations of Amino Acids in Plasma of Lactating Cows During the Experimental Induction of Ketosis¹

Departments of Dairy²
and Chemistry, New Mexico State Univesity³, Las Cruces 88003

ABSTRACT

Amino acids in plasma of 12 cows were determined during 10 days to measure effects of a lowenergy ration and exogenous thyroxine. Cows were fed rations which provided either their energy and protein requirements on Day 0, or only 30% of the energy and 90% of die protein required. A daily dosage of 6.9 mg of Lthyroxine (sodium) pentahydrate injected on Days 4 through 7 in combination with the lowenergy ration induced signs of clinical ketosis. The combination of thyroxine injections with a low-energy ration elevated valine, leucine, and isoleucine on Day 5. These were much lower on Day 7. These changes were similar to those of the pattern of glucose in blood. Glutamic acid was highest on Day 6. These changes in amino acids were apparently the result of protein catabolism in response to energy deficiency. Possible causes for the elevation of tiiese amino acids in plasma, and the possibility of these amino acids having triggered a release of insulin are discussed. In addition, some possible metabolic deficiencies are discussed considering commonly established biochemical pathways.

¹ Journal Article 421, Agricultural Experiment Station, New Mexico State University, Las Cruces.

⁴ Present address: P.O. Box 122, Albion, Washington 99102.