Ammoniating Crop Residues as a Feed Resource

Ammoniating Crop Residues as a Feed Resource

September 2012


photo - covered stack of ammoniated wheatstraw

In drought conditions, forages that are harvested in the summer are not as productive and yield is reduced. A practice for producers to consider is ammoniating low quality forages to be used later as a feed resource to stretch other harvested forages when cows are not grazing.

Ammoniating of Low Quality Forages

Ammoniating low quality forages is a management technique that can be used to treat forages like wheat and oat straw and baled cornstalks. It is not recommended to be used on grass hay, summer annuals, and alfalfa.

Toxicity can occur when medium quality forages are ammoniated and fed to cows and the calves who's dam consume ammonia treated forages. The toxic compound is transferred through the milk to the calf. Affected calves walk in circles and this is commonly referred to as circling disease. If toxicity occurs in the calves or cows, avoid working or moving the cattle and remove the forage. To my knowledge, circling disease has not occurred in cattle as a result of consuming ammoniated straws or crop residues.

Treating wheat straw with anhydrous ammonia can make straw almost as digestible as average quality prairie hay. Ammoniating will increase digestibility of low quality forages and, therefore, intake will increase. Cattle don't quit eating straw because they don't like it; but, because of its low digestibility and slow rate of passage, they can't stuff anymore into their rumen.

The ammoniation process is temperature dependent and occurs faster at higher environmental temperatures.

  • If the temperature is 86EF, the ammoniated residue needs to be kept sealed for one week.
  • If the temperature is between 59EF and 86EF it needs to remain sealed for 2 to 4 weeks.
  • If the temperature is below 59EF, the ammoniated forage needs to be sealed for 4 to 8 weeks.

It is important to keep the package sealed and not let the ammonia escape. It can be difficult to keep the package sealed for a long period of time because of wind and curious pets and wild animals.

For residues like wheat straw, bale the straw soon after grain harvest, preferably with some moisture on it or bale early in the morning when there is some dew present.

To prepare an area to ammoniate, scrap an area that will accommodate three big round bales wide with 5 to 6 feet on either side and in the front and back and 10 to 12 bales long. Push the dirt to the sides of the area where the bales will be stacked. The dirt will be used to seal the plastic around the edges.

Gather bales into rows that are stacked in a pyramid (three bales on the base, two bales on the second level, one bale on the top or three bales on the base and two bales on the second level) leaving a couple of inches between pyramids for the ammonia to filter around the bales. Cover the entire stack with one sheet of 6 to 8 millimeter black plastic. If the plastic is 40 by 100 feet, you will be able to cover 10 to 12 pyramids in a row. Make sure the edges of plastic on the ground are sealed with loose soil to prevent leaking of ammonia. Any holes in the plastic can be patched using duct-tape.

Place a pipe (6 to 8 feet long) on the ground and insert it into the center of your stack. Next, attach the pipe to the anhydrous tank and slowly leak anhydrous into the bales sealed with plastic. Ammonia can be dangerous so be careful when working with this product. Don't inject ammonia too fast or the plastic can rupture. Continue to add anhydrous slowly until you have added 60 pounds per ton of residue on a dry matter. This process will take about 10 minutes for each ton of forage ammoniated. When completed, turn off the tank, remove the pipe, and seal its opening with dirt. Keep the stack sealed to allow for the reaction to be completed. About a week before feeding, open one end of the stack to allow excess ammonia gas to escape.

If you sample treated straw and conduct a nutrient analysis, the crude protein content of the treated straw will be greater than the non-treated straw. To measure protein content of a feed/forage, the analysis measures the NH3 groups present in the sample and because NH3 groups were added through the ammoniating process, it stands to reason that crude protein content of the treated straw be higher. Some of the NH3 in the treated straw will be used by bacteria in the rumen to make bacterial protein.

More importantly than the increase in crude protein content is the increase in digestibility by about 10% of the treated straw compared to the untreated straw. The increase in digestibility of the treated residue allows cattle to consume more of the treated residue compared to non-treated straw by about 20%. This allows the animal to meet a greater portion of their nutrient needs by consuming the treated forage.

To determine the cost of ammoniating low quality residue, use local prices. If anhydrous ammonia is priced at $400 per ton then it is $.20 per pound. Remember treatment calls for 60 lb of anhydrous per ton of straw DRY MATTER. The calculations would go something like the following: If the stack were arranged in pyramids (3 bale base, 2 bales on top) 14 bales long, there would be a total of 84 bales. If each straw bale weighed 1000 pounds, there would be 42 ton of straw. If the straw were 90% dry matter, there would be 37.8 ton (42 tons x .90 = 37.8 tons dry matter) of straw dry matter. In this example you will need 2,268 pounds of anhydrous. The cost of anhydrous is $12 per ton, plastic will cost $7 per ton, labor will be $3 per ton, machinery costs will be $1.70 per ton, and miscellaneous costs will be $.36 per ton for a total ammoniation estimated cost, not including the residue, of $24 per ton.

For more information, please see the Ammonia Treatment of Low Quality Forages document (PDF 89KB). The document includes a Worksheet to Determine the Amount of Anhydrous to Add and data on various residues.

By Rick Rasby
Beef Specialist - University of Nebraska