Download What is NPN in feed, How does it work

What is NPN in feed, How does it work
Non-protein nitrogen (NPN) compounds are used by rumen bacteria of cattle and
sheep. Studies show that these compounds are broken down to ammonia during the
fermentation process in the rumen. The microorganisms combine the ammonia with
metabolized carbohydrate products to form amino acids, and thus, proteins. The bacteria and protozoa, plus the protein they contain, are digested by the animal further
down the digestive tract. Simple stomach animal such as pigs and chickens cannot use
NPN in large amounts because of the lack of bacteria and enzymes to break down the
NPN to ammonia and synthesize it into proteins.
The most common source of NPN used in feeds is urea. Other products include biuret ( a slow release NPN),
ammonium sulfate and ammonium chloride which is commonly used to prevent urinary calculi. In the laboratory, crude protein is determined by analyzing for nitrogen. Protein averages 16% nitrogen. Therefore, the percent nitrogen multiplied by 6.25 gives the percent crude protein analysis. Thus, urea with a 45% nitrogen has a
protein equivalent of 281% (45 x 6.25) for ruminants. If a protein supplement contains crude protein from nonprotein nitrogen not more than 12%, then the supplement contains 4.27% urea (12/281 x 100 = 4.27%).
Urea is highly soluble in the rumen and microorganisms decompose it rapidly to ammonia and carbon dioxide.
Therefore, conditions in the rumen need to be favorable for microorganisms to use the ammonia from urea
before it escapes the rumen. If the ammonia builds up in the rumen faster than it can be converted to microbial
protein, it is absorbed through the rumen wall into the blood stream which is then carried to the liver. The liver
detoxifies by converting ammonia to urea and then excreted. However, if ammonia builds up too rapidly, the
liver capacity is exceeded and ammonia spills into the main blood stream and can cause toxicity.
The amount of urea to use for cattle will depend upon the number of microorganisms in the rumen, how rapidly they are growing, and whether other essential nutrients and ammonia are available when needed. For fast
growth, microbes need minerals, vitamins and a source of readily available energy. Thus, more ammonia is
used when cattle are fed high energy type feeds. Starch from grain is the best source of energy. Cattle on highgrain rations can derive a larger percentage of their protein from urea than cattle on just roughage rations. Energy from roughages is made available slower in the rumen, and therefore, the microorganisms do not make as
good of use of the ammonia from urea.
Urea in feeds is normally used to reduce the cost of cattle rations. Urea has protein value, but not energy, vitamins and minerals. It takes about 0.68 pounds of urea (281), 4.5 pounds of corn, 0.1 pounds of dical. And 0.17
pounds of potassium chloride to furnish about the same amount of nutrients in 5 pounds of soybeam meal
(46%). These amounts can be used to figure if urea or soybeam meal will supply protein equivalent more
cheaply in cattle rations.
When feeding cattle, plant protein supplement should be fed the first 25 days. This can lessen the lag period
that often occurs when cattle are started on urea supplements. Don’t feed urea supplements to shipped cattle
that have been off feed for two or three days. Urea should not supply more than one third of the protein equivalent in the total ration. Cattle on moderate-energy growing rations should limit urea to 0.15 pounds a head
daily. Urea must be mixed uniformly through the feed to prevent over-consumption of urea by individuals.
As for horses, Microbial activity takes place in the cecum and colon of the horse. Therefore, non-protein nitrogen is absorbed from the small intestine and excreted in urine before it reaches the cecum and colon to be
used as protein synthesis. That which does reach the cecum and colon may be used for protein synthesis,
much of that protein is unavailable to the horse and is excreted in the feces.
Research has shown that intakes of feed to horses containing 14% protein equivalent from urea (5%) as the
total diet and providing as much as 0.5 pounds of urea daily did not have detrimental effects on mature horses. This amount is several times greater than the toxic amount for cattle. Therefore, horses may be fed diets
containing urea made for cattle. However, the non-protein nitrogen compound in the feed is of little benefit
to the horse. The amounts in these feeds are not harmful.
Since little of the non-protein nitrogen is utilized by the horse, this amount should be
subtracted for the crude protein content of the feed. If the feed tag states that it contains 25% crude protein with 12% crude protein equivalent from non-protein nitrogen,
then the feed provides 13% crude protein for the horse. The 12% crude protein equivalent from non-protein nitrogen has no benefit or harm to the horse.