Pyruvate Metabolism in the Dairy Calf

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Abstract
Two male Jersey calves were used in evaluating procedures for a detailed study of pyruvate metabolism. One calf was fed a high-carbohydrate diet composed of dried skim milk, dried whey, cerelose, salts, and vitamins A and D; while the other one was fed whole milk containing 3.5% fat. The amount of Cl4 recovered in the expired CO2, the rate of CO2 excretion, and the maximum radioactivity in the respired CO2 were similar in both calves during three hours following the intravenous injection of pyruvic acid 2-C14 . The C14 incorporated into liver glutamic acid, aspartic acid, alanine, and glycine, after correcting for dose and animal size, was higher 24 hours after the injection in the whole-milk fed calf than in the one fed the semi-synthetic diet. The distribution of C14 within glutamic acid isolated from liver protein indicated that relatively more pyruvate was incorporated into the glutamate via the CO2 fixation route involving oxalacetate than via the acetyl-CoA route on whole milk than on the high-carbohydrate diet. These limited data indicated that carbohydrate was utilized more extensively for the synthesis of intermediates of the citric acid cycle when a high-fat diet was consumed than when a high-carbohydrate diet was fed.