Content
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WHAT IS UREA (NH2)2CO
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HOW IS UREA MADE &
MECHANISM OF UREA UTILIZATION
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USES OF UREA
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UREA POISONING
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RECOMMENDATIONS FOR UREA FEEDING
WHAT IS UREA (NH2)2CO ?
1. Urea is a simple and organic compound that contains 46.7 % nitrogen which is equivalent
to 292 protein (Urea-true) and 42-45% nitrogen equivalent for 262 – 281 for feed grade
urea.
2. It is found in many plants and is a normal end product of protein metabolism in mammals.
3. A part of the urea produced in the animal’s body is returned to the digestive tract in the
saliva and by absorption through the rumen wall. The remainder of the urea is passed off in
the urine as waste.
4. Urea serves an important role in the metabolism of nitrogen-containing compounds by
animals and is the main nitrogen-containing substance in the urine of mammals.
5. It is solid, colourless, and odorless (although the ammonia that it gives off in the presence
of water, including water vapor in the air, has a strong odor).
6. Urea which is relatively cheap chemical product, is such a non-protein nitrogen.
7. It should be realized, that NPN (urea) can only be used in low level production systems
with high amounts of poor quality roughage.
8. These compounds can provide nitrogen for ruminants which can be incorporated into
amino acids and thus become part of a protein.
9. It is highly soluble in water (neither acidic nor alkaline) and non-toxic.
10. Urea is rapidly converted into ammonia in the rumen by the action of water:
(NH2)2CO + H2O ---> 2NH3 + CO2
Urea
ammonia
Figure 1 Urea
HOW IS UREA MADE?
Urea is made by reacting carbon dioxide (CO2) with anhydrous ammonia (NH3) under pressure of
3000 psi and temperatures of around 350 deg F. Water is removed during processing and the
molten matter is either converted to prills or into granules.
Mechanism of urea utilization
1. When urea from feed sources enters the rumen, it is rapidly dissolved and hydrolyzed to
ammonia by bacterial urease.
2. The ammonia can then be utilized by the bacteria for synthesis of amino acids required for
their growth.
3. Amino groups are also split from amino acids and from intact proteins and used by bacteria
in the same manner.
4. Protein synthesis within the rumen by micro-organisms is very closely associated with the
activity of these same organisms in breaking down cellulose and other carbohydrate
materials and in the formation of organic acids as by-products of this fermentation process.
5. The solubilities of natural proteins vary greatly and thus the rate at which they are
hydrolyzed and utilized by bacteria differs appreciably.
6. fairly high proportion of the more soluble proteins such as casein will be utilized by
bacteria in about the same way as the ammonia from urea.
7. For the less soluble proteins such as zein, the process of ammonia liberation is much less
rapid and fairly large proportions of the protein may pass through the rumen to the
abomasum without being broken down.
8. When ammonia is produced too rapidly in the rumen or if the concentration becomes too
high, appreciable amounts are absorbed directly into the bloodstream, reconverted to urea
in the liver, excreted through the kidneys in the urine and thus lost to the animal.
9. There is, however, always a small amount of urea in the bloodstream and other body fluids.
This urea finds its way into the saliva and re-enters the rumen. Urea has been shown to pass
into the rumen directly through the rumen wall from the circulating blood.
USES OF UREA
 Urea is a protein replacement
 Drought feeding for survival
 Supplementing low quality pasture
 Supplementing low quality rations (hand-feeding) for maintenance
 Supplementing green pasture forage
 Maintenance of breeding cows and ewes
 Feeding growing and fattening lambs
 Feeding weaner cattle for growth
 Preparing beef cattle for fattening
 Fattening cattle in feedlots
 Spraying pastures
 Urea in salt licks or salt blocks
 Addition of urea to silage
 Addition of urea to hay
UREA POISONING
1. Must be treated quickly (within minutes to two hours after consumption).
2. The poisoning occurs when the ingested urea exceed the rumen’s capacity to convert it
(urea) into ammonia, of which is used for produce microbial protein. The rumen has a
limited capacity to convert ammonia to microbial protein.
3. The maximum limit of conversion is considered to be 30 g - 32 g N per kilogram of
digestible matter.
4. Excess ammonia may accumulate in the rumen and absorbed across the rumen walls into
the bloodstream and it is then converted to the urea in the liver and excreted into urine
(pathway can easily be overwhelmed and excess ammonia and urea circulate in the blood,
causing poisoning ) if given above maximum limit of conversion.
5. Cattle become accustomed to metabolising urea, but if they miss out for a couple of days
and are then allowed sudden access, or if they consume more than normal, then poisoning
can occur.
6. Urea is very soluble and dissolves rapidly into puddles of water, which can form on blocks
after rain. Cattle that lick up these puddles can consume excess urea.
7. It is recommended that urea should provide no more than 2% - 3% of the concentrate
ration, or 1% of the total feed intake and no more than one third of the total nitrogen intake
should be NPN.
8. In cattle 0,3 g/kg - 0,5 g/kg (for example: 120 g - 200 g for a 400 kg cow) is considered to
be toxic and 1 g/kg - 1,5 g/kg (for example 400 g - 600 g for a 400 kg cow) can be fatal.
9. Signs of poisoning :
 twitching of ears and facial muscles
 grinding of teeth
 frothy salivation
 bloating
 abdominal pain
 frequent urination
 forced rapid breathing
 staggering
10. Often, animals are just found dead near the source of the urea supplement.
Recommendations for Urea Feeding
The inclusion rate of urea should not exceed 1,5% of the feed intake. Animals should be adapted to
the NPN-containing diet by:
• Starting cattle gradually on urea supplementation and increasing it slowly to about 0,1 g/kg body
weight (35 g - 40 g for a 400 kg cow).
• Ensuring that cattle get regular daily access to supplementation, once started.
• Restarting cattle at a lower intake level, if they unavoidably miss out on urea supplementation for
a couple of days.
• Preventing over-consumption of supplement mix or blocks (like using salt to regulate intake).
• Feeding supplement mixes or blocks under a roof, to prevent urea getting wet and dissolving.
Feedlot Rations
Feed no more than:
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Up to 15 to 25 percent of total crude protein (CP) in cattle and sheep fattening rations.
0.1 to 0.25 pound urea per head per day to cattle.
0.28 to 0.70 pound CP per head per day to cattle.
Up to 0.5 to 1.0 percent urea in total air dry beef ration (90 percent dry matter). Current
recommendation is 0.7 percent urea. Feeding higher levels of urea will cause lower feed
intakes, lower daily gains, poorer feed conversions, longer feeding period and less profit.
Dry Cows
Feed no more than:
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
0.05 pound actual urea per cow per day.
0.14 pound protein equivalent from urea per cow per day.
Supply no more than 20 to 33 percent of total nitrogen in supplement from urea when: 1) feeding
harvested roughages and 2) feeding low protein supplements to cows grazing dry winter range. It
is best not to feed urea in high protein supplements (40 percent CP) to cows on winter range. If this
is the practice, be sure that urea contributes less than 10 percent CP equivalent.
Lactating Cows
Feed no more than:
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0.05 to 0.10 pound actual urea.
0.14 to 0.28 pound protein equivalent from urea.
Calves
Do not feed urea to 300- to 450-pound calves.
Table 1: Maximum amounts of urea that should be fed to yearlings and calves.
Pounds of urea per day
Concentrate content of the ration, %
Yearlings
Calves
81-100
0.25
0.20
61-80
0.20
0.17
40-60
0.15
0.14
Less than 40
0.12
0.10
Yearlings: 650 pounds and heavier
Calves: 450-650 pounds