Influence of Site of Administration of Urea on Voluntary Intake of Concentrate by Lactating Cows

Abstract

Four rumen-fistulated cows were fed isonitrogenous diets in a Latin square design with 14-day periods. Treatments were: Control (C), urea-oral (UO), urea-rumen (UR), and urea-abomasum (UA). Concentrates fed C, UR, and UA cows contained I% urea while that fed UO cows had 370. Sufficient urea in an aqueous solution (1:5) to equal 270 of the concentrate intake was placed twice daily directly into the rtmaen of UR cows or into the abomasum of UA cows. Concentrate was offered ad libitum just before urea administration, and hay (5.4 kg) was fed once-a-day. Daily intakes of concentrate were similar for C (13.3 kg), UR (12.6 kg), and UA (13.1 kg) treatments but depressed for UO (10.6 kg) (P < .05). Treatment did not affect average concentrations of blood urea nitrogen or blood ammonia. Intake depression on high-urea diets is due to the undesirable taste of urea and not to ruminal or post-ruminal effects. In a second experiment dissolution of urea in molasses masked the undersirable taste of a concentrate containing 3.570 urea and resulted in slightly higher intakes than a concentrate supplemented with soybean meal and molasses and higher (P < .05) than when urea was not dissolved in molasses before mixing with other dry concentrate ingredients.