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The Utilization of Urea Nitrogen by Young Dairy Calves¹

University of Kentucky, Dairy Section, Lexington

Abstract

Thirty-six, 2-day-old male and female calves (18 Jerseys and 18 Holsteins) were raised to 86 days of age on a limited milk-hay-starter system to study the value of urea as a source of nitrogen for young dairy calves. Three experimental starters were used: Starter 1 (low protein) 6.7% protein; starter 2 (urea supplement) 15.1% protein equivalent; and starter 3 (conventional-protein supplement) 15.2% protein. Urea supplied 54.2% of the nitrogen in starter 2.

All groups of calves grew at comparable rates for the first 6 weeks during which time whole milk was being fed. When whole milk feeding was discontinued, the urea-supplemented and conventional-protein groups grew at a significantly faster rate than the low-protein group. These two groups consumed significantly more feed and had significantly higher feed efficiency values than the low-protein group. Differences between the conventional protein group and the urea-supplemented group in average daily gain, starter consumption or pounds of feed required per pound of gain, were not significant.

Calves on the low-protein ration digested a significantly smaller percentage of protein and crude fiber and retained less nitrogen than either of the other two groups. Calves on the urea ration digested a lower percentage of crude fiber than those on the conventional protein ration. The results show that a portion of the nitrogen requirements of the young calf can be supplied in the form of urea.

Cud inoculation of calves had no value as measured by growth, feed consumption, apparent digestibility or nitrogen retention.

¹ The authors express their appreciation to Lederle Laboratories, Pearl River, N. Y. for supplying the Aureomycin supplement and to Allied Dye and Chemical Corp., New York, N. Y. for supplying the urea used in this study. The investigation reported in this paper is in connection with a project of the Kentucky Agricultural Experiment Station and is published by permission of the Director.

^₂ Present address: Dairy Department, Michigan State U., East Lansing, Michigan.