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Ruminal Fermentation Products and Plasma Ammonia of Fistulated Steers Fed Apple Pomace-Urea Diets

U.S. Department of Agriculture, Beltsville, MD 20705

Abstract

The effects of apple pomace diets on ruminal fermentation products and plasma ammonia (NH₃) were studied in two trials with fistulated steers. In trial 1, four fistulated steers were used in a 4 x 4 Latin square designed experiment to compare the addition of starch, trace minerals or both to an apple pomace-urea diet. In trial 2, five fistulated steers were used in a 5 x 5 Latin square designed experiment to compare a corn silage diet, an apple pomace-cottonseed meal diet, an apple pomace-urea diet, an apple pomace-urea diet plus corn starch and an apple pomace-urea diet plus straw. Feeding apple pomace was associated with a slightly reduced ruminal pH, a higher acetic propionic acid ratio, lower proportions of ruminal butyric, isobutyric and isovaleric acids and a noticeable production of ruminal ethanol. After apple pomace diets were fed, ruminal acetic acid increased more rapidly than propionic acid and ruminal ethanol concentration increased to a peak about 2 hr after feeding. The apple pomace-urea diet elevated ruminal NH₃ concentrations and tended to delay the normal ruminal NH₃ peak with time after feeding; however, plasma NH₃ concentrations were not elevated. The addition of starch to apple pomace-urea diets tended to lower the acetic propionic acid ratio and to increase butyric acid. The effect of starch on ruminal NH₃ concentration was variable but tended to lower the concentrations. Ruminal NH₃ concentration peaked sooner with time after feeding when a mixture of trace minerals was added to the apple pomace-urea diet. The addition of straw to the apple pomace-urea diet did not affect ruminal fermentation products.

¹ Ruminant Nutrition Laboratory, Nutrition Institute, Science and Education Administration, Beltsville, MD 20705.