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Cooperative Extension System
Cattle Producer's Library
Cow-Calf Section CL1150
efficiency, weight gain, and cow body condition can be
improved.
Treatment of straw with anhydrous ammonia (nonprotein
nitrogen, NPN) raises the crude protein content
of ammoniated forages. Keep in mind that NPN is not
utilized as efficiently as natural protein. It has been
shown that unless some form of energy supplement is
fed in conjunction with the ammoniated straw, a utilizable
crude protein value of 6 percent should be used
when balancing rations for beef cattle. One other benefit
of the ammoniation process is that ammonia acts as
a preservative of high moisture forages by inhibiting
mold growth.
The majority of ammoniation research has been done
with straws because of their low protein and usually
lower feeding value. Research has been done by Dan
Doornbos et al. (1985) at the Northern Agricultural Research
Center in Montana. His research involves feeding
beef heifers during the winters of 1983-84 and 1984-
85. The heifers, weighing about 500 pounds, began a
140-day feed trial after a short grazing and warmup
period after fall weaning.
One group received the traditional growing ration
fed at the rate of 20 pounds of corn silage, 2 pounds of
rolled barley, and 5 pounds of alfalfa hay per head. The
other group received 7 pounds of ammoniated wheat
straw, 4 to 6 pounds of rolled barley, and 5 pounds of
alfalfa hay per head daily. Growth goal was to gain 1.25
to 1.5 pounds daily so the heifers would breed normally
as yearlings.
During the first winter's trial, temperatures were very
low. Average daily gain of the heifers on corn silage
dropped but was still in the target range. Gain of heifers
on the ammoniated straw ration fell below a pound
per day, however. They ate all they could, but rate of
Managers faced with the lack of pasture and highpriced
feed during drought conditions look for alternatives
to their usual methods of wintering beef cattle.
Those who have wheat or barley straw may find that
ammoniation could solve their winter feeding problems.
Ammoniation is a method of treating low-quality
roughages to improve their nutritional value for ruminant
animals. The method involves sealing this forage
in a gas-tight, enclosed container and adding anhydrous
liquid ammonia to the forage. This method can also be
used to some extent to prevent molding of crop residues
or high-moisture forages. At about 21 days, the
chemical action is complete, and this product can be
used for feed.
Benefits of Ammoniation
Due to a high lignin content, straw is poorly utilized
by ruminants. Ammoniation (sealing the forage in an
air-tight system and injecting anhydrous ammonia) of
crop residues can be a practical and economically feasible
method of improving the feeding value of straw
for beef cattle.
Ammonia treatment increases laboratory dry matter
digestibility of straw 8 to 15 percentage units. By disrupting
the fiber structure of the plant during the ammoniation
process, greater rumen fermentation is allowed.
Along with increased forage digestibility is an
increase in the amount of forage dry matter that a cow
can physically consume. Daily dry matter intake of straw
can be increased 15 to 20 percent through ammoniation.
With higher forage digestibility and intake, feed
1This process has not been cleared by the FDA as an approved
practice. Users of this practice do so at their own
risk.
One Method of Ammoniated
Straw for Beef Cattle1
Roger Brownson, Beef Cattle Specialist
Montana State University
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passage of the straw limited intake. Once the weather
warmed, the heifers compensated with gains of up to 2
pounds a day for a while. Heifers gained an average of
1.37 pounds per day on the ammoniated straw ration.
Those on the corn silage ration averaged 1.68 pounds
of daily gain.
The cost of gain with the ammoniated straw ration
was 40.7 cents per pound; for the silage ration, 33.4
cents per pound. These heifers then were pastured together
and artificially inseminated during a 21-day period.
Cleanup bulls were used for 23 days. Pregnancy
rates were the same for heifers fed both rations.
Doornbos et al. (1985) found that the heifers got going
as easily on ammoniated straw as those on corn silage.
The economics of an ammoniated straw ration depend
upon the availability of anhydrous ammonia and
straw. In areas where there are large amounts of small
grains, the use of anhydrous ammonia could become
practical.
In general, ammoniation improves feeding quality
by increasing the amount of total digestible nutrients
(TDN) available in the straw. It improves the amount
of roughage that animals will consume, and it increases
the crude protein equivalent.
Straw intended for ammoniation should contain at
least 12 percent moisture, preferably 15 to 20 percent.
Greater moisture allows more nitrogen in the feed. The
feeding quality of the straw should be as follows:
• Wheat straw should have TDN value of at least 33
percent.
• Barley straw TDN value should be at least 38 percent.
You should submit a sample to a feed testing laboratory
to assure the moisture content and feeding quality
of your straw for adequate ammoniation. Moisture content
can be determined by on-farm testing kits.
When to Ammoniate
The efficiency of ammoniation depends on temperature.
The higher the temperature, the better the results.
Generally it is advisable to ammoniate early in the fall
before temperatures become too cold. As mentioned, a
relatively high moisture level is necessary for efficient
ammoniation. This can be achieved by baling early in
the morning after a heavy dew, or by baling as soon as
possible after a rainfall. Another alternative, of course,
is to add water to the straw as it is baled.
Location for Ammoniation
Each stack or bale should be downwind some distance
from buildings and cattle holding areas. Stacks
should be accessible to farm machinery from all sides.
Accessibility to both ends is important so that ammoniation
pipes can be inserted. It is also useful to have
enough shelter to reduce or prevent wind damage of
the stacks.
Covering the Stacks
The size or dimension of the straw stacks is determined
by the size of the plastic sheet one can purchase.
Six mil black polyethylene is available in various
widths. The most useful sheets are 100 feet long by 40
feet wide. Stacks or piles can be constructed so that the
overhang on each side is at least 2 feet, so the plastic
can be sealed properly at the ground.
Hand-built bale stacks or bale wagon stacks can be
used. Round bales can be stacked in rows, and chopped
straw can be piled on the bales and covered with a sheet
of plastic.
Any type of silo should be suitable for ammoniation
if the ammoniated gas can be well dispersed throughout
the straw. A trench silo is useful, because it requires
less plastic per ton of straw and helps hold the heat generated
by the ammoniation treatment.
When covering the stack, take care to avoid puncturing
the plastic. Choose a day with no more than a
light breeze blowing.
It may be advisable to hoist the roll onto the stack
with a farmhand and unroll the plastic along the top of
the stack and unfold it down the sides. In some cases it
may be best to unroll the plastic on the ground and drag
it over the stacks.
When the plastic has been positioned over the stack,
place dirt or sandbags along one side. Tighten the plastic
down on the other side and cover it. Then pull out
the corners as if wrapping a parcel and fold across the
end of the stack. Tape down all edges and pile dirt
around all sides. Finally, if possible, cover stacks with
a fishnet or camouflage net to avoid wind damage.
Determining How Much Ammonia to Add
When 3.0 percent anhydrous ammonia, based upon
the dry matter content of the residue, is added, let's assume
that the stack to be ammoniated contains 1,500
bales weighing an average of 43 pounds each, and that
the average moisture content of the straw is 12 percent.
Dry wt of straw =
No. of bales x avg. bale wt x (100 - % moisture)
OR
1,500 bales x 43 lb x (100 - 12%) =
56,760 lb or 28.38 tons
56,760 lb x 3.0% = 1,703 lb of NH3
Volume of NH3 required =
wt of NH3 (lb) x density of NH3
5.15 lb/gal
OR
1,703 lb = 330.7 gallons (This method
5.15 lb/gal would require a metered pump.)
If a nurse tank is used, determine the pounds in each
1 percent and reduce the percent as shown on the gauge
the appropriate amount.
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After calculating the amount of ammonia to add,
uncover a 3-foot length of plastic along the base of the
stack half-way down one side. This allows air to escape
from the enclosure as ammonia evaporates. Thus,
the pressure within the enclosure does not build up, and
anhydrous ammonia can be added more rapidly.
Pressurized liquid anhydrous ammonia is hazardous.
This operation should be carried out by an experienced
ammonia dealer. It is important to add the correct
amount of ammonia. Too much means unnecessary
expense, and too little will create a poor quality feed.
About 20 to 30 minutes after the ammonia has been
added, the pipe can be removed. Be sure to wear goggles
and insulated rubber gloves for protection from the
ammonia residue.
As mentioned, ammonia process is complete in about
21 days. Leave the stack covered until a few days before
the ammoniated straw is required for feeding. When
opening the stack, be careful for exposure to ammonia
gas that may still be present. Open the stack on a day
when there is a slight breeze blowing away from the
buildings and corrals. Leave the stack for a few days to
allow all excess ammonia to evaporate. Animals will
not consume feed that has a strong odor of ammonia.
The cost of treating straw with ammonia depends on
the cost of the materials. These materials vary from year
to year and within location. If materials are purchased
at a competitive price and a large stack is treated, your
cost for ammoniation could range from $12 to $17 per
ton.
When formulating rations for either cattle or sheep,
consult the drought guide sheets for that purpose.
Ammoniation
Canadian researchers recommend using only iron
pipes (Fig. 1). The pipe is pushed through the plastic
with a tractor and adjusted so that holes point down to
enable the pipe to drain free of liquid ammonia. Insert
the pipe until it is just past the hole nearest the "T".
Insert pipes into both ends of the stack if the stack is
more than 20 feet long. Forty feet would be ideal with
the 22-foot pipes sticking in each end.
References
Kernan, J., and J. Knipfel. No date. Ammoniation of straw
and chaff, Factsheet, Agriculture Canada Swift Current
Research Station.
Doornbos, D. E., D. C. Anderson, and D. D. Kress. 1985.
Anhydrous ammonia treated straw. In: A growing ration
for beef heifers. Proc. Western Section American Society
of Animal Science. p. 120.
Fig. 1. Details of ammoniated pipe about 22 feet long.
Issued in furtherance of cooperative extension work in agriculture and home economics, Acts of May 8 and June 30, 1914, by the Cooperative
Extension Systems at the University of Arizona, University of California, Colorado State University, University of Hawaii, University of Idaho, Montana
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opportunity in education and employment on the basis of race, color, religion, national origin, gender, age, disability, or status as a Vietnam-era
veteran, as required by state and federal laws. Second edition; Fall 2000 Reprint