Urea and Other Nonprotein Nitrogen Compounds in Animal Nutrition (1976) / Chapter Skim
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USE OF UREA AS A PROTEIN REPLACEMENT FOR RUMINANTS
USE OF UREA AS A PROTEIN REPLACEMENT FOR RUMINANTS
Pages 17-29
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From page 17... ...
In addition to the amino acid needs of the host, there are nitrogen requirements for the microbiota if the ruminant is expected to use forage and other cellulose-containing energy sources, if the biological system is to synthesize nutrients not ordinarily added to the diets (such as B vitamins) , and if the microbiota are to be used to detoxify dietary ingredients that may contain or be contaminated by chemical residues.
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From page 18... ...
However, it has been demonstrated many times that urea is a satisfactory source of supplementary protein in diets for ruminants that have low total dietary protein requirements (maintaining a mature ruminant)
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From page 19... ...
By contrast, the protein-supplemented cattle were not similarly influenced with respect to TON intake. In the feedlot, those cattle receiving urea supplements often have lowered performance during the initial weeks than those receiving protein supplements; however, subsequent performance is improved.
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From page 20... ...
There may be production situations where it would be economically feasible to accept a lower rate and efficiency of performance and use urea for all of the supplemental needs in diets of animals having high protein requirements. DIETARY FACTORS AFFECTING MICROBIAL PROTEIN SYNTHESIS An optimal level or concentration of the following factors will maximize rumen microbial synthesis: ammonia, readily available energy, carbon skeletons, minerals, vitamins, growth stimulators or inhibitors (antibiotics, hormones, anabolics)
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From page 21... ...
- The efficiency of nitrogen or ammonia utilization will be greatest whenever ammonia is the first-limiting factor necessary for synthesis. For example, urea utilization will be high in low-available nitrogen diets that contain abundant levels of available energy, carbon skeletons, minerals, vitamins, and other components that enhance microbial activity.
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From page 22... ...
These attempts each predict that in highconcentrate diets with TON values in excess of 75 percent on a dry matter basis, some ammonia will be synthesized into additional microbial protein at protein levels below 12 or 13 percent. At higher protein levels in these high-concentrate diets, the formulae predict that ammonia from protein breakdown will adequately support maximum microbial growth and that ammonia from added NPN will not further enhance microbial synthesis and therefore will not be useful.
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From page 23... ...
SOURCES OF CARBON SKELETONS The main sources of carbon chains for microbial synthesis are from fermented carbohydrates and preformed dietary amino acids. The degraded proteins are the main source of the branched-chain carbon skeletons.
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From page 24... ...
Although a low level of antibiotic supplementation in ruminant diets is often reported to have a favorable influence, it is difficult to indicate specifically the mode of action of the beneficial effect-if there is one. Urease Inhibitors Ruminal hydrolysis of urea usually occurs at a faster rate than subsequent microbial utilization of the liberated ammonia (Bloomfield et al., 1960)
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From page 25... ...
Chemical inhibitors do not presently appear to offer much promise for improving urea utilization. FEEDING PROCEDURES TO IMPROVE UREA USE ADAPTATION Retention of nitrogen by ruminants fed urea sometimes appears to increase with length of the feeding period until a plateau is attained.
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From page 26... ...
found essentially the same performance from lambs fed twice or 12 times daily soybean meal-supplemented diets. However, he found that feeding urea-supplemented diets twice daily produced negative nitrogen balances that were positive when urea was fed 12 times daily.
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From page 27... ...
LIQUID SUPPLEMENTS These products are primarily molasses-based materials with urea or other NPN compounds as the major nitrogen source plus an array of minerals. Their use has become increasingly widespread in recent years because of the availability and price of ingredients used and the convenience of handling and feeding liquids.
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From page 28... ...
There appears to be no substantial effect of these substances on the microbiota in the rumen. SUMMARY AND CONCLUSIONS Since dietary urea is used as a source of nitrogen for microbial protein synthesis, which in turn furnishes amino acids for the host animal, it is apparent that nutritional management must be considered that will maximize microbial protein production.
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From page 29... ...
The addition of urea to forage at ensiling time is a convenient method of urea supplementation to silage diets. The use of liquid supplements as a method for supplementing the diet with urea has several advantages, such as furnishing available energy for the microbiota that are necessary in urea utilization, providing a delivery system for micronutrients and other dietary additives, and improving nutrition management to insure diet uniformity and reducing losses due to dust and wind erosion.
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