ANN 121: Applied Animal Nutrition-I (2+1)

UREA

• Urea is non-protein nitrogen compounds which are recognised as useful sources of nitrogen for ruminant animals.
• Their use depends upon the ability of the rumen microorganisms to use them in the synthesis of their own cellular tissues and they are thus able to satisfy the microbial portion of the animal’s demand for nitrogen and, by way of the microbial protein, at least part of its nitrogen demand at tissue level.

          
NH₂

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C=0

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NH₂

• Pure urea has nitrogen content of 46.6% which is equivalent to a crude protein content of 46.6 x 6.25 = 291%

• Urea is hydrolysed by the urease activity of the rumen micro organisms with the production of ammonia.
• The ease and speed with which this reaction occurs when urea enters the ruminant gives rise to two major problems owing to excessive absorption of ammonia from the rumen.
• Thus wastage of nitrogen may occur and there may be a danger of ammonia toxicity.
• This is diagnosed by muscular twitching, ataxia, excessive salivation, tetany, bloat and respiration defects.
• Urea should be given in such a way as to slow down its rate of breakdown and encourage ammonia utilisation for protein synthesis.
• The diet should also contain a source of readily available energy so that the microbial protein synthesis in enhanced and wastage reduced.
• Urea, like other non-protein nitrogen sources, will not be used efficiently by the ruminant animal unless the diet does not contain sufficient degradable protein to satisfy the needs of its rumen microorganisms.
• Although urea provides an acceptable protein source, there is evidence that where it forms a major part of dietary nitrogen, deficiencies of the sulfur-containing amino acids may occur.
• In such cases supplementation of the diet with a sulfur source may be necessary.
• An allowance of 0.13 g of anhydrous sodium sulfate/per gram of urea is generally considered to be optimal.
• Urea does not provide energy, minerals or vitamins for the animal, and when it is used to replace conventional protein sources, care must be taken to ensure that satisfactory dietary levels of these nutrients are maintained by adequate supplementation.
• Supplementation of the diet with a sulphur source may be necessary to achieve a nitrogen, sulphur ratio not wider than 15:1.