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Urea Utilization by Sheep in the Presence of Potassium Nitrate^{1, 2,}

University of Missouri, Columbia 65201

Abstract

DURING a winter experiment (December to March) finishing lambs receiving soybean meal supplemented rations made better gains and were more efficient than lambs receiving urea. During a summer experiment (June to September) lambs receiving urea performed equally as well and in most instances better than lambs receiving soybean meal.

The simultaneous addition of 2% KNO₃ and 1% urea decreased average daily gain (ADG), feed utilization and thyroid activity in finishing lambs receiving a high concentrate ration (P>.05). These effects occurred whether KNO₃ was introduced before or after urea and were overcome after an adaptation period of approximately 21 days.

Lambs supplemented with urea had significantly higher plasma urea-N levels than the soybean meal supplemented lambs in experiment I (December to March) but not in experiment II (June to September). There was a tendency for finishing lambs receiving KN03 plus urea or soybean meal to have a slightly higher plasma urea-N level than their counterparts receiving urea or soybean meal only. Methemoglobin never exceeded 2.2% of the hemoglobin.

These results indicate that from a toxicity standpoint, it is not necessary to remove urea from properly supplemented high concentrate rations when 2 % KNO3 is being consumed by sheep. However, some adaptation to non-protein nitrogen (NPN) is necessary. Proper nutritional and management practices must be followed, especially during the adaptation period.

¹ This investigation was supported by Farmland Industries, Kansas City, Missouri. The authors express their appreciation especially to Dr. B. W. Beadle of this organization.

² Contribution from the Missouri Agricultural Experiment Station. Journal Series No. 6407. Approved by the Director.

³ Present address: Department of Animal Husbandry, University of Tennessee, Knoxville 37916.

⁴ Department of Animal Husbandry.