Ammonia Treatment Of Low-Quality Forages

By Justin Waggoner

Millions of tons of crop residue and other low-quality forages are produced every year in the United States. However, because of their bulkiness, relatively low energy and protein feeding value, and value for covering the soil, little of this abundant feed source is utilized for livestock. Ammoniation is a procedure designed to increase the energy availability of low-quality forages such as wheat, barley and oat straw, corn or grain sorghum stover, and very mature warm-season grasses. Research over the last few decades has demonstrated that ammonia treatment of low-quality roughages will substantially improve digestibility, voluntary intake, and cattle performance. Most forages with less than 5 percent crude protein and 45 percent TDN (total digestible nutrients) on a dry matter basis are candidates for ammonia treatment. Ammoniating higher quality forages is not advised, therefore it’s important to test any materials taken off the field to ensure the crude protein is not above the recommended range.

How does ammoniation improve forage feeding value?

Ammoniation increases the digestibility of crop residues and grass hays by breaking lignin-cellulose bonds in plant fiber, thereby swelling the plant tissue to allow greater microbial activity, and improving dry matter digestion (TDN) by 8 to 15 percentage units.

Ammoniation boosts feed intake by 15 to 20 percent or more because of improved forage digestibility and increased rate of passage through the digestive tract. Ammoniation usually doubles crude protein content by being a non-toxic source of non-protein nitrogen (NPN) and it is well utilized by calves and cows. Ammoniation preserves forage that contains up to 25 to 30 percent moisture because it kills molds and fungi and prevents heating which reduces feed losses.

Techniques of ammonia application

The most common and consistently successful means of treating dry forages with ammonia has been to cover the material with 6 mil black plastic sheeting, sealing the plastic against the ground with soil, crushed rock, or other material. Enough fill should be placed to keep the plastic from being pulled loose by winds and when the ammonia gas fills the stack cover like a balloon.

Traditionally, a 3% application of anhydrous ammonia (dry weight) has been recommended (60 lbs anhydrous ammonia/dry ton hay). However, research conducted a K-State demonstrated that lower application rates (1.5% dry weight or 30lbs anhydrous ammonia/dry ton hay) produced proportionally greater improvements in both crude protein and in-vitro dry matter digestibility. The results of this study are summarized in Table 1 and the full report may be accessed online in the 2014 K-State Cattleman’s Day report http://hdl.handle.net/2097/17779.

Table 1. Nutrient composition and estimated cost/value of wheat straw prior to (PRE) and following application of 1.5% or 3.0%  anhydrous ammonia on a dry basis. 

¹Treatment with 1.5% (HALF) or 3.0% (FULL) dry weight basis of anhydrous ammonia.
^*Linear P < 0.01, Quadratic P = 0.02
^a,b,c,  Within a row, means without a common superscript differ (P ≤ 0.10)
^† Linear P < 0.01, Quadratic P = 0.10

Apply the ammonia slowly (for three to five hours) into the center of the stack.. Producers should weigh a few bales to estimate gross weight of the stack. If the moisture content is 15 percent, dry matter weight will be 85 percent of the gross weight. A slow application of ammonia is best as it permits the liquid to fully volatilize, reducing the amount lost in the soil.

Producers should build the stack and estimate the total dry forage for treatment. The exact amount of anhydrous ammonia can be ordered, and the ammonia can be applied until the tank is empty. After starting the application, producers should check the cover for leaks and apply duct tape to any holes in the plastic.

For best results, crop residues and other forages should be covered and ammoniated as soon after harvesting as possible to minimize weathering and dry matter losses maximizing feed value. The time needed for maximum treatment effect may range from only a few days in 90˚F plus weather to 30 to 45 days during cold winter temperatures. Anhydrous ammonia will seek the moisture in the stacked forage which aids in the uniform spread of the ammonia. Eight to 10 percent is an adequate forage moisture content, but 15 to 25 percent is preferred. The ammoniated stack should remain covered until two weeks before feeding when the cover is opened to allow bales to air out to reduce the concentration of residual ammonia.

Consider the cost of ammoniating forages

Producers should also be advised that the costs associated with ammoniating wheat straw have increased. A 40 x 100-foot roll of 6 mil black plastic will cost approximately $325 and anhydrous ammonia is was as much as $1400/ton back in July in some locations. At these July prices the cost/value of wheat straw treated with the 1.5% and 3.0% application rates is $107 to $128/ton respectively. Anhydrous ammonia has dropped a little in price since July but not enough to significantly reduce the final cost when ammoniating forages. At these values, producers should evaluate what other forage options are available before making the decision to ammoniate wheat straw as other comparable, cost-effective forage options, such as grass hay, may be available.

Safety considerations

Anhydrous ammonia is maintained under pressure and can be dangerous. If misused, it can burn skin, eyes, or throat and can explode and burn. Follow these precautions:

• Wear goggles, rubber gloves, and protective clothing
• Work upwind when releasing anhydrous ammonia
• Have fresh water available to wash off any anhydrous ammonia that comes in contact with the skin
• Check all valves, hoses, and tanks for leaks
• Check the plastic cover on the stack for leaks and seal any holes with duct tape
• Do not smoke near anhydrous ammonia
• Keep children away from the treatment area

The possibility of ammonia toxicity with cattle fed ammonia-treated forages appears remote. Studies have been conducted with application rates of over 6 percent ammonia to dry forages without illness or harmful side effects to ruminants. The ammonia odor of freshly uncovered treated forages also acts as a safety factor. Research has shown that animals will not eat ammonia-treated crop residues unless they are aerated or mixed with a fermented feed so that the silage acids neutralize the ammonia. Ammoniated forages should have the end of the plastic cover removed and allowed to aerate for two weeks before feeding.

Summary

Ammonia treatment is a very effective means of markedly increasing the feeding value of low-quality forages. Do not treat with ammonia any higher quality forages. Large crop acreages offer an almost unlimited supply of lower quality crop residues which can be transformed into relatively nutritious forages with the potential of improving the economy of cattle production.