Animal Husbandry Notes – For W.B.C.S. Examination – On Use Of NPN In Ruminants.

পশুপালনের নোট – WBCS পরীক্ষা – রুমিনাসগুলিতে এনপিএনের ব্যবহার।

Review was carried out on the use of different nitrogen sources in ruminant nutrition. Non-protein nitrogen (or
NPN) is a term used in animal nutrition to refer collectively to components such as urea biuret uric acid and a
number of other ammonia compounds which are not proteins but can be converted into proteins by microbes in
the ruminant stomach. Urea is a simple compound that contains 46.7 percent of nitrogen compared to 16 percent
for most proteins. There is no question but that urea and other non protein nitrogen substances can be fed safely
to ruminants to replace part of the dietary protein.Continue Reading Animal Husbandry Notes – For W.B.C.S. Examination – On Use Of NPN In Ruminants.

When urea with feed sources enters the rumen, it is rapidlydissolved and hydrolyzed into ammonia by bacterial urease. The amount of urea included in concentratemixtures for cattle or sheep should not exceed 3 percent and usually the addition of 1 to 1.5 percent will proveadequate. In the total ration, the amount of urea should not exceed 1 percent. At these levels of intake, urea has
proved an effective for growing and fattening beef cattle and for dairy cattle Urea may cause toxicity and evendeath in ruminants if it isfed inadequately mixed with other feeds or in too large a dose. The toxic signs caneasily be recognized. The slow-release of nitrogenfrom biuret is better matched to the energy in the diets ofcattle consuming low-quality forages, thus improving the utilization of forage and reducing the metabolic cost ofeliminating excess nitrogen in urea-based diets. Dried poultry waste (DPW) contains an contains true protein andhigh amount of NPN in the form of rumen degradable uric acid. Uric acid can be utilized by rumen microbes forprotein production. Poultry manure can safely be supplemented to ruminant animals for considerable increase in
performance.

The primary aspect distinguishing ruminants and non-ruminants is of course the difference in their digestive
systems. Non-ruminants can digest only real proteins and use only them in their body, while ruminants can
utilize all nitrogen compounds (Burgstaller, 1983). It is known that NPN compounds make, among many feeding
materials, of 20-30% of the whole nitrogen in field grass, 50% of the nitrogen in silages and 40-50% of the
whole nitrogen in the containing segments of especially things like roots, nodes, onions and the ratio decreases
as the plants ripen (Ozgen, 1978; Burgstaller, 1983). Ruminants are capable of utilizing different protein sources
due to their stomach physiology. Rumen microorganisms synthesize protein from substances containing nitrogen
to build up their cells and ruminants use this aspect of the microorganisms to satisfy some and sometimes all of
their need for proteins from nonprotein nitrogen compounds (Kirchgessner, 1985). Animals with simple
stomachs (pigs and chickens) cannot make use of large concentrations of NPN compounds because of a lack of
enzymes and bacteria to break down the NPN to ammonia and synthesize it into protein.
Protein rich leguminous forages are not widely grown in many areas grazed by ruminants, and
vegetable protein supplements are usually expensive or unavailable. Among the problems facing the livestock in
the tropics is the low protein tropical grasses and the high cost of alternate sources of protein such as the
Soybean and other oil cake. Feeding grass, fodder and concentrates of low nutritive value doesn’t always meet
the nutritional needs of ruminants, hence they should be replaced with suitable alternatives in feed one of such
alternative is the use of non-protein nitrogen (NPN) compounds. A portion of nitrogen in feeds for ruminants
may be provided in the form of simple nitrogen compounds (non-protein nitrogen / NPN) that are degraded in
the rumen to release ammonia (NH3), which is used by rumen microorganisms to produce amino acids (Nadeem
et al. 2014). It has long been recognized that supplemental nonprotein nitrogen (NPN) is most efficiently utilized
in rations low in protein and relatively high in digestible energy. It isalso widely accepted that supplemental
NPN is utilized better when small rather than large amounts are added to ruminant rations (Satter and Roffler,
1977).
The ability of the micro-organisms in the rumen of cattle and sheep to utilize these NPN sources to
form true protein that can be converted to meat and milk by the animals represents an important contribution to
human’s food supply. The objective of this paper was to review the different non protein nitrogen sources and
their importance in ruminant nutrition.

The Different NPN Sources
Non-protein nitrogen (or NPN) is a term used in animal nutrition to refer collectively to components such as urea
biuret uric acid and a number of other ammonia compounds which are not proteins but can be converted into
proteins by microbes in the ruminant stomach (Wikipedia, 2015). NPN could also be defined as nitrogenous feed
nutrient that are not bound together by peptide bonds and are found within or outside the animal’s body system.
All NPN’s generate ammonia in the rumen which enters the liver and finally converted to urea.
2.1. Urea the most common NPN
Urea is the principle commercial source of NPN for use in ruminant diets. Urea is a simple compound that
contains 46.7 percent of nitrogen compared to 16 percent for most proteins. When plant protein feeds, such as
soybean meal, are high priced, it is economical to use urea as a protein supplement in ruminant rations. Urea, the
cheapest solid nitrogen source, is a white crystalline water-soluble powder that is used as a fertilizer. Urea
contains 46% nitrogen; thus each kilogram of urea is equivalent to 2.88 kg of crude protein (6.25 x 0.46), which
in most rations equals a digestible crude-protein content of 200%. To improve the flow characteristics, urea is
processed into feed-grade urea (42% nitrogen), in which each grain of urea is covered with kaolin or some other
non-hygroscopic substance. One kilogram of urea plus 6 kilograms of maize or other grain furnishes the same
amount of nitrogen as 7 kilograms of soybean meal or an equivalent high-protein feed, but it-may be lower in
energy content since urea adds no useful energy
The cheaper fertilizer urea can be use, however, when mixed with liquid feeds or even in solid feeds if
added in the form of a suspension or solution in molasses. Urea stops bacterial growth and fermentation in
concentrations over 10% but it has a very bitter taste and limits intake if used at high levels. It has been known
for quite a long time that urea can be recycled and used as a source of nitrogen for the rumen microorganisms
(Stanton & Whittier 1998).
When urea with feed sources enters the rumen, it is rapidly dissolved and hydrolyzed into ammonia by
bacterial urease. The ammonia can then be utilized by the bacteria for synthesis of amino acids required for their
growth (Panday, 2010). Urea is commonly incorporated into various supplements designed for feeding dairy
cattle, beef cattle, and sheep.
The most important applications of urea in the true pastoral areas, are usually during periodic severe
droughts (Morris (1958). Morris (1958a) stated that supplements of wheat and urea improved the survival rate
and increased the roughage intake. Ryley (1961) found that with the small addition of sorghum, urea reduced
body weight loss, improved birth weight of calves, reduced neonatal mortality, and led to higher milk yields and
calf growth rate. Beames (1963) has reported the conditions that the addition of urea to the ration enabled the
animals to survive during drought. An earlier study by Harris and Mitchell (1941) showed that lambs could gain
in body weight and store body nitrogen on rations containing 40 to 65 percent of the nitrogen in the form of urea,
the rates of gain were less than desired for efficient lamb fattening operations.
Urea is fed as a replacement for a part of the protein in a ration. The ability of microorganisms present
in the rumen of ruminants, use of feeding urea reduces the need for imported protein supplements with no
deleterious effects on the animal. Treating with urea is based upon its transformation into ammonia. The amount
of urea included in concentrate mixtures for cattle or sheep should not exceed 3 percent and usually the addition
of 1 to 1.5 percent will prove adequate (panday, 2010). Urea toxicity has been documented many times and is
characterized by an over-consumption of urea containing feeds or feeding of urea without a suitable fermentable
carbohydrate source. Primary causes include: Poor mixing of feed, Errors in ration formulation, Inadequate
period of adaptation, Low intake of water, Feeding of urea in conjunction with poor-quality roughages, Low
feed intake prior to exposure to feed containing urea and Rations that promote a high pH in rumen
fluid(Blezinger, 1998). It appears to be great scope here for supplementing the low quality forage available
during the dry season where beef cows are exposed to nutritional stress during pregnancy or lactation, which
may seriously impair their lifetime productivity. As the level of urea increased, average milk production and
body weights decreased and the efficiency of nitrogen utilization decreased somewhat. Cows can consume as
much as 272 grams of urea in their daily feed without evidence of any adverse effect. The cows produced an
average of 21.3 kilograms of 4 percent fat-corrected milk per day on a concentrate mixture containing linseed
meal plus 1.2 percent of urea, 20.7 kilograms on soybean meal, and 20.6 kilograms of milk on a mixture of
soybean meal and linseed meal. The basal ration consisted of cereal grains, wheat bran and molasses as
concentrates and grass hay and maize silage for roughage.

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