Ammoniating Straw

Michael Fisher, Golden Plains Area Livestock Extension Specialist

 

As drought continues to wreak havoc on forage and crops throughout the region, the price of feeding livestock keeps increasing.  Those in the animal agriculture industry are looking for feed alternatives and ways to lower their input costs.  Recently, some producers have been asking about ammoniating straw in an effort to extend their forage resources.  Ammoniating straw requires that anhydrous ammonia be pumped into a sealed stack of low quality forage and allowed to bind with the forage tissue.  This is a process that was researched and came to be an accepted management strategy many decades ago; however, it is often only used in desperate times.  Ammoniation requires added labor and supply inputs.  It can also be hazardous to the environment, livestock, and producers if mismanaged.  Additionally, as the spread between hay prices and anhydrous ammonia prices widens, the ammoniation option becomes less economically favorable.


It is important to point out that ammoniation does not improve the forage itself, but adds a non-protein nitrogen (NPN) source to the straw.  In many cases, this should increase both the intake (17 to 18 percent) and digestibility (20 percent) of low quality forage.  It is commonly accepted that the crude protein (CP) content of ammoniated forage can be 1.5 to 2 times greater than the same non-ammoniated forage, when the process is done properly.


There is a small range of forages that are acceptable candidates for ammoniation.  Usually it is the grass family (wheat, oats, etc.) that make for suitable candidates.  Their tissue is easily permeated by the anhydrous ammonia and binds with the moisture within the tissue.  Ammonia hydroxide is formed in this process and becomes the NPN source.  Legumes (alfalfa, beans, etc.) should not be ammoniated.  They have a more complex lignin & fibrous carbohydrate structure that interferes with the process.


The forage being ammoniated needs to have a moisture content of 15 to 20 percent.  Otherwise, the ammoniation process will not complete itself.  Often, straws will have lower moisture levels than this.  Water can be added to increase the moisture content but needs to be done according to research established guidelines.  If done incorrectly, molds can form and ruin the modified feed source.
Nutrient content of the forage being ammoniated can also limit successful candidates.  An initial CP level of 3 to 6 percent is recommended.  Below 3 percent CP and there is not enough improvement to justify the expense of ammoniation.  Additionally, research has shown the starting neutral detergent fiber (NDF) content of the forage should be from 70 to 80 percent.  When NDF exceeds 80 percent, there is once again not enough economical benefit to justify the process.  Forages that have better quality than 6 percent CP and 70 percent NDF often have higher free sugar content within the tissue.  When ammonia interacts with these, toxic compounds can be formed; rendering the forage useless.


The actual ammoniation process is a slow procedure.  The straw stack has to be prepped with anhydrous lines and sealed.  Typically, it will take a couple of days to slowly apply the anhydrous ammonia.  Application should only be done in daylight hours.  In routine August weather you should expect the interior temperature to reach 160*F.  This should allow the chemical reaction to occur over 7 days.  Cooler September environments may take 14 days or more for the chemical reaction to occur.


Only about 18 to 25 percent of the anhydrous ammonia applied to the straw will actually become fixed within the tissue.  The remaining ammonia will volatize and be trapped under the plastic.  As the plastic is removed, this gaseous ammonia is released into the atmosphere and can be very dangerous to those individuals working around the ammoniated straw stack.  Caution must be used when removing plastic from this feed source and a safety spotter should always be utilized.


Those readers wanting information about the application procedure or the mathematical equations that should be used in formulating your ammoniation plan may want to read “Ammoniation and Use of Ammoniated Low Quality Forages” (CL 382) in the Cattle Producer’s Library.  It can be accessed online at http://www.ansci.colostate.edu/beef/info/cattlemanslibrary/382.pdf.

 

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