Urea and Other Nonprotein Nitrogen Compounds in Animal Nutrition (1976) / Chapter Skim
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FEEDING UREA-CONTAINING DIETS TO BEEF CATTLE, DAIRY CATTLE, SHEEP, AND GOATS
FEEDING UREA-CONTAINING DIETS TO BEEF CATTLE, DAIRY CATTLE, SHEEP, AND GOATS
Pages 38-87
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From page 38... ...
. It has been pointed out that, although urea oftentimes is a satisfactory supplement, nevertheless, under some conditions, it is not a satisfactory source of supplementary nitrogen for beef cattle, even though conventional recommendations for urea use are followed.
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From page 39... ...
Thus, in each experiment where a greater animal response was observed with either urea or protein supplementation, it was assumed that the negative control diet was inadequate in protein and that supplementation was needed to satisfy the animal's protein requirements. SUBMAINTENANCE AND LOW-ENERGY BEEF CATTLE DIETS Experimental evidence indicates that supplementary urea is beneficial to submaintenance as well as low-productivity beef cattle diets with less than 60 percent TON in their DM and composed almost exclusively of low-quality roughages with less than about 7-8 percent protein.
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From page 40... ...
29(1 949) : 173-1 84 4.5 66 6.8 Yes Yes Iowa State Univ.
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From page 41... ...
R195(1974) :l-9 7.7 74 10.4 Yes Yes Iowa State Univ.
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From page 42... ...
urea, however, was less effective in increasing nitrogen retention. In a wintering trial, pasturing 2-year-old steers on dry prairie grass, these authors reported equal performance between a cottonseed meal supplement and one containing one-third urea and two-thirds cottonseed meal nitrogen.
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From page 43... ...
fed Hereford heifers a sorghum silage diet containing an estimated 4.9 percent protein and 57 percent TON on a dry matter basis. During the 28-week feeding period, animals without supplementation lost weight, while those receiving urea gained.
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From page 44... ...
(1960) reported benefits from urea supplementation of veld forage containing 6 and 6.7 percent protein and 54 percent TON on a dry matter basis.
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From page 45... ...
fed a diet containing an estimated 8 percent protein and 54 percent TON in the dry matter and received no significant benefits from urea supplementation. Similar results were obtained byO'Bryan(1960)
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From page 46... ...
fed a basal diet estimated to contain 66 percent TON and 5 percent protein in the dry matter and composed of fresh sugarcane plus a small amount of corn grain. Cattle receiving the basal diet lost weight, contrasted with the cattle receiving the basal diet supplemented with urea.
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From page 47... ...
an unsupplemented corn silage diet estimated to contain 70 percent TON and 8.4 percent protein on a dry matter basis, (2) unsupplemented corn silage treated with 0.5 percent urea, (3)
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From page 48... ...
No negative control diet without supplementation was fed. The diets, before supplementation on a dry matter basis, were estimated to contain 73 percent TON and 9 percent protein.
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From page 49... ...
In one trial with untreated and unsupplemented corn silage, steer calves gained moderately well while consuming the basal diet containing 10.2 percent protein and an estimated 73 percent TON on a dry matter basis. Steers fed a similar diet supplemented with urea or soybean meal gained 7 and 16 percent greater, respectively.
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From page 50... ...
The diets, when urea and soybean meal were not considered, contained an estimated 10 percent protein and 67 percent TON on a dry matter basis. Live-weight gains were similar, as were digestibility data collected on the three diets.
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From page 51... ...
In at least 26 experimental trials reported in the literature, cattle were fed high-productivity diets in which negative control diets devoid of urea were fed. Benefits from urea resulted in all experiments when the basal diet contained less than 11 or 12 percent protein on a dry matter basis or less than 13.5-14.5 percent on a TON basis (Table 1)
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From page 52... ...
Loosli and McCay (1943) fed a corn grain, cornstarch, cane molasses, and timothy hay basal diet containing an estimated 4 percent protein and 82 percent TON on a dry matter basis to young calves.
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From page 53... ...
(1949) fed two basal diets containing an estimated 10 percent and 10.7 percent protein and 77 percent TON on a dry matter basis.
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From page 54... ...
Protein supplementation of nearly all high-productivity diets was superior to urea supplementation when the unsupplemented basal diet contained less that 11-12 percent protein on a dry matter basis. One obvious reason why a unit of supplemental urea nitrogen should be somewhat inferior to a unit of supplemental protein nitrogen is that only about 80 percent of the total urea nitrogen converted into rumen microbial nitrogen is alpha amino protein (Hungate, 1966)
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From page 55... ...
Less-important diet considerations, such as sulfur deficiency, rumen microbial adaptability, and poor palatability characteristics of urea, doubtlessly exert some influence upon utilization; but the amount appears to be relatively minor in the case of beef cattle. SUMMARY AND CONCLUSIONS This review of more than 100 beef cattle reports revealed an orderly picture of benefits from urea supplementation when the experiments were grouped in accordance with the energy and protein levels present in the unsupplemented negative control basal diets.
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From page 56... ...
Medium-energy diets are defined as those containing between 60 and 75 percent TON in the dry matter, and often they contain mixtures of forages and grain. Supplemental urea regularly improved most of these diets with or without readily available carbohydrates being present in the supplement, provided less than 10 percent protein was in the diet dry matter and provided the diet before supplementation had insufficient protein to meet the cattle's body needs.
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From page 57... ...
In a European review, Rys (1967) points out that utilization of urea nitrogen occurs when basal diets are deficient in protein.
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From page 58... ...
also compared pelleted starter diets containing 1.1, 2.2, and 3.3 percent urea added to a negative control of 7.1 percent protein. Daily gains were highest in calves fed the diet containing 2.2 percent urea.
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From page 59... ...
Diets 1 and 2 contained about 18 percent protein. Calves fed the urea and 18 percent SBM diet gained 0.60 kg/day; negative controls gained 0.52 kg/day (P< 0.07)
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From page 60... ...
Negative control diets containing 6 and 7 percent protein and supplemental diets of urea, ammonium bicarbonate, and casein at 20 percent protein in one trial and graded levels of urea from 1.4-4.3 percent in a second trial raised total diet protein levels to 19.4. Although some overfeeding of protein was apparent, growth response and carcass analysis clearly demonstrated that urea was used by these cattle, although not as efficiently as casein.
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From page 61... ...
(1968) compared the effects of feeding urea-corn silage (0.5 percent urea)
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From page 62... ...
Because of the capacity of highproducing dairy cattle to mobilize both energy and nitrogen from body reserves for milk production, nitrogen balance trials are helpful to establish the nutritional status of lactating cows fed urea-containing diets. It is also important to describe the specific conditions of the study, such as the number of times per day animals are fed and characterization of the diets with respect to their content of major and trace minerals and other factors.
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From page 63... ...
(1968b) on the production and reproductive performance of highproducing Holstein cows fed concentrate mixtures containing 0 or 1.5 percent urea.
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From page 64... ...
The diets contained 15.9, 15.9, and 16.8 percent protein, respectively. The animals were fed the diets during a 35-day preliminary period, a 7-day adjustment period, and a 105-day comparison period.
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From page 65... ...
Total milk production ranging from 16 to 24 kg/day and persistency were increased by additional energy and depressed by increasing urea level. In the third experiment, concentrate mixtures (18 percent protein)
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From page 66... ...
Nitrogen balance data revealed that the cows fed the 0.85 percent urea-corn silage were in negative nitrogen balance because of low protein digestibility and high urinary nitrogen losses. These results emphasize the need for production trials of long duration, negative controls, and balance data for evaluating the effect of urea on milk production.
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From page 67... ...
Feed intake was lower for cows fed the urea-treated 44 percent dry matter silage. Since milk production of the cows fed untreated silage plus 16.2 percent protein concentrate was similar to those receiving the 22 percent protein concentrate or urea-treated silage, it was impossible to determine the extent of urea nitrogen use because the negative control cows may have been depleting body protein reserves during the trial.
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From page 68... ...
Cows were adjusted to urea previous to the study. In the first experiment, urea was not well used in either 12, 17, or 22 percent protein concentrate mixes (1.5 percent urea)
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From page 70... ...
plus concentrate (14 percent protein, 1 percent urea)
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From page 71... ...
Feed intakes and milk yields of cows fed the urea silage, ammonia silage, and positive control diets were all similar and significantly greater than for the cows fed the negative control diet. Milk production averaged 25.7 kg/day for the cows on the experimental diets compared to 19.4 kg/day for the negative controls.
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From page 72... ...
The liquid supplement was fed at two levels to supplement a basal diet composed of pelleted concentrate (1 percent urea) and corn silage ad libitum.
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From page 73... ...
requirement for sulfur by lactating cows is given at 0.2 percent of the total diet, which implies an N:S ratio of 12:1 for medium-producing cows (15 percent protein in the total diet dry matter)
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From page 74... ...
reported that a pelleted mixture containing 66 percent dehydrated alfalfa, 31.6 percent urea, 2 percent dicalcium phosphate, and 0.4 percent sodium metabisulfite or sodium propionate makes a very effective substitute for soybean meal in diets of lactating cows. When cornmeal and oats were combined with about 9 percent of this pellet, a concentrate mixture containing 19 percent protein and 2.84 percent urea was obtained.
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From page 75... ...
also reported a significant increase in milk production when a gelatinized milo-urea mixture or a urea-dehydrated alfalfa combination was compared to a control diet containing 2.5 percent urea. These preliminary results indicate that a urea-dehy combination and an extruded urea-grain product may partially resolve one problem of feeding urea; namely, poor acceptance of the urea diet and perhaps a more constant release of ammonia in the rumen.
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From page 76... ...
Over 1 percent urea in the complete feeds did not adversely affect intake or production. The protein solubility of feeds in the basal diet can have a marked effect on rumen ammonia levels and the usefulness of added urea to the diet.
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From page 77... ...
Total diet soluble nitrogen should also be considered, because both corn silage (Johnson et al., 1967) and hay crop silage (Waldo, 1968)
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From page 78... ...
No significant differences were observed in intake or body measurements. The total diets contained from 11.2 to 14.6 percent protein, with the urea diets containing the higher level, so that some of the nitrogen was probably unneeded.
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From page 79... ...
Corn silage plus alfalfa grass silage was blended with the concentrate premix to provide a complete ration. The heifer diets were 12 percent protein and were changed 2 weeks before calving to lactation diets of 54 percent silage and 46 percent concentrate (dry basis)
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From page 80... ...
Consumption, however, does not necessarily mean effective use. Utilization of urea is improved by: • A level of protein in the basal diet that is below the requirement.
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From page 81... ...
In terms of actual amounts, 1.5-2.0 percent urea in the grain mixture under general conditions or 1 percent of the total diet dry matter are good general guidelines for lactating cows, or 200-250 g/day. When highmoisture hay crop silage is the primary forage, and/or when this forage is fed with fermented grain, these levels should be reduced by at least one-half.
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From page 82... ...
have shown that urea is a useful source of nitrogen in diets containing no more than 12 percent protein. With sheep fed purified urea-containing diets (Hume et al, 1970)
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From page 83... ...
A possible explanation was that the high-concentrate, soybean meal-supplemented, 10 percent protein diet was not sufficiently degraded in the rumen to supply adequate nitrogen for rumen microbial synthesis of necessary nutrients such as B vitamins, while the high-concentrate, urea-supplemented, 10 percent protein diet may have provided sufficient rumen ammonia levels for adequate microbial synthesis. However, at higher protein levels, Braman et al.
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From page 84... ...
amino acids of microbial protein for supporting nitrogen balances in growing lambs. However, there have been conflicting reports regarding the value of free unprotected dietary amino acids.
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From page 85... ...
For example, the favorable responses to high-grain, high-protein diets may be due, in part, to some rumen bypass of the dietary protein and starch. As indicated earlier, the ideal practical feeding diet might be one containing sufficient NPN to sustain an active rumen microflora that (a)
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From page 86... ...
The most favorable responses from urea supplementation have occurred in diets containing relatively high concentration of readily fermentable carbohydrates and relatively low dietary levels of total nitrogen12 percent protein equivalent or less after supplementation. High levels of urea and/or urea fortification of high-nitrogenous diets have often depressed performance by reducing diet acceptability or by reducing nitrogenous utilization.
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From page 87... ...
fed a sorghum grain supplement containing 4 percent urea once daily to goats grazing poor-quality pasture in Mexico and observed some decrease in milk production. This might have been predicted with such a readily soluble compound fed at that level once daily.
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