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Urea May Cause Death Loss of Cattle New employees may not know about the dangers of feeding modern feedlot supplements that contain urea or other sources of "crude, protein from non-protein-nitrogen (NPN)." They may not know that proper mixing of rations is critical to get top cattle performance. Here are a few notes about feeding urea and NPN supplements that may be helpful for teaching employees about this potential problem. Suggestions For Feeding Urea can cause toxicity and death loss. Caution is needed when feeding urea or urea containing supplements. Urea is very soluble in the rumen; therefore it is immediately available for the rumen bacteria. If ruminant animals eat excess urea, ammonia toxicity will occur. In feedlot rations: For feedlot and confined operations, urea supplements and premixes need to be mixed with other feed ingredients to insure proper dispersion in the ration. Urea for pastures supplementation. When pellets or range cubes are fed, the aggressive animals may get more than their share. If the pellets or cubes contain urea, ammonia toxicity may occur. Prevention of this may be achieved by feeding protein blocks or like tubs to achieve small intakes. For safety reasons, it is my experience that all-natural protein range cubes are an excellent choice. However if urea-containing supplements are used for pasture feeding, caution is needed when feeding, so the aggressive animals do not consume more than their share. Why Does Urea Work as a Protein Source The urea supplied to ruminant animals is called "crude protein from non-protein-nitrogen." This is often just called NPN. The reason urea works for feeding out animals is urea contains ammonia just like the ammonia that is released from the natural protein sources like soybean meal. The ammonia from urea is released in the rumen by urea enzymes and then the rumen bacteria capture the ammonia to build bacterial protein. Ultimately the bacterial protein is digested in the small intestine just like the natural protein from the other feed ingredients in the ration. Urea is Efficient Some of the protein in hay and silage is tied up in the cell wall of the forage and is unavailable for digestion. But since urea is soluble, all is available for turning it into the protein of the rumen microbes. Urea must have plenty of energy to make it work efficiently. Therefore, urea works best in confined feeding operations where grain is fed. Urea also works more efficiently if supplied in each of the daily feedings. Urea and Nitrates Urea and nitrates are both nitrogen chemicals, but are very different. Both are toxic if consumed in excess. It takes only a small amount of nitrate to cause death loss. Urea (ammonia) toxicity is a brain poison, while nitrate toxicity causes death by tying-up oxygen in the blood. The blood turns brown color with nitrate toxicity. The problems of feeding either urea or feeds that contain nitrates are overcome by feeding with energy feeds like grains and mixing or diluting with other feed ingredients. Ammonia Sources Other Than Urea Urea is not the only source of crude protein from non-protein-nitrogen in modern feedlot rations. Ammonium sulfate and ammonium phosphate are common ingredients to feedlot supplements. There are also several ammoniated molasses products that are available. Ammonia is often used to lower the acidity of some products. Caution is needed when feeding high ammonia products to prevent reduced intake or death loss. Alfalfa silage contains up to 40% of the crude protein as ammonia in solution. All silage contain considerable soluble protein that breaks down to ammonia in the rumen Test Rations for Protein and NPN of the Mix One of the most important tests for quality control of rations is the test of crude protein. Supplements and premixes need to be checked for NPN as well as crude protein. Your nutritionist will work with you in establishing the values. |
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