Ammoniation of Forages

Producers faced with the problems of storing damp hay or wishing to improve the feeding value of low quality forages can consider ammoniation as the solution. Ammoniation serves two main purposes:

  • Ammonia (NH3), which contains nitrogen, increases the crude protein content of feed. It further increases the feeding value by assisting in the breakdown of the poorly digested lignin fraction of mature forages.
  • Ammonia also acts as a preservative, allowing producers to safely harvest forages at higher moisture levels. Overheating is prevented as bacteria and moulds are destroyed during the ammoniation process. This results in a safer and more palatable end product, with less destruction of plant nutrients during storage. Field harvesting losses and the dependency upon the weather are also reduced.

Factors Affecting the Response to Ammoniation

Percent moisture in the roughage, the time of ammoniation, temperature and amount of anhydrous ammonia applied are the key factors affecting forage response to the ammoniation process.

Anhydrous ammonia binds to water molecules in the roughage. Without adequate moisture, binding, and therefore improvement in feeding value, cannot occur.

Prior to ammoniation, analyze a representative sample of the roughage for moisture content. A minimum level of 12 per cent moisture is essential. Knowing the moisture level in the forage is also essential for determining the amount of NH3 to be added.

When looking at the time factor, the benefits of ammoniation are increased if it is done soon after harvesting. Forages which remain in the field undergo weathering, decreasing both the nutritive value of the forage and its response to ammoniation.

When using ammonia as a preservative for high moisture hay, stack and treat the hay as quickly as possible, as heating will start occurring immediately. Only bale a volume of feed that can be stacked, covered and ammoniated in a-day.

Temperature determines the speed at which the reaction between ammonia and the feedstuff occurs, as well as the extent of improved digestibility. Higher temperatures result in faster reactions and a greater increase in digestibility. When the temperature decreases, the length of time required to complete the reaction is increased and the increase in digestibility is not as marked.

The per cent improvement in crude protein is dependent upon the amount of anhydrous ammonia applied to the forage.

Effect of Ammoniation on Nutrient Levels

Results from Manitoba Agriculture and Food projects show increases in crude protein content ranging from 85 per cent to 125 per cent following ammoniation at 3.0 per cent of forage dry matter (See Table 1).

Table 1: Changes in per cent crude protein following ammoniation with three per cent NH3 by weight on a dry matter basis.

Percent Crude Protein



Percent Improvement

Barley Straw 5.1 9.4 84
Wheat Straw 4.2 8.6 105
Oat Straw 3.2 7.2 125
Slough Hay 8.2 15.8 93
Wheat Chaff 7.4 12.7 72

Source: J. Gramiak, Manitoba Agriculture, Food and Rural Initiatives

Analyze feed for crude protein content before and after ammoniation. This allows for determination of economic feasibility. The analysis after ammoniation is also essential in formulating balanced rations.

Increases in digestibility, measured as total digestible nutrients (TDN), also occur when roughages are ammoniated. The increase in TDN can be determined by an in vitro analysis only.When formulating rations, an increase in TDN of 10 to 15 per cent after ammoniation should be allowed for. For example, straw with a TDN value of 45 per cent before ammoniation could be assumed to have a TDN value of 49.5 per cent following ammoniation.

Results from the Agriculture Canada Research Station in Melfort, Saskatchewan show that the per cent mould is significantly reduced and intake of high moisture hay improved following ammoniation. This corresponds with results from the Swift Current . Research Station and Manitoba Agriculture and Food projects also show ammoniated forages to be a palatable feed for dairy and beef cattle (Table 2).

Table 2: Effect of ammoniation on forage intake and weight gain by pregnant beef cows (Swift Current Research Station).


Untreated +4.95 lb oats +3.08 lb alfalfa pellets

Ammoniated +4.95 lb oats

Roughage Intake (lb/day) 9.68 14.52
Bedding Consumed (lb/day) 7.04 6.6
Total Roughage Intake (lb/day) 16.72 20.90
Weight Gain (lb/cow/day) 0.31 1.43

Source: Ammoniation of Straw and Chaff, Kernan and Knipfel. Publication No.453, University of Saskatchewan.

Untreated +2.25 kg oats +1.4 kg alfalfa pellets

Ammoniated +2.5 kg oats

Roughage Intake (kg/day) 4.40 6.6
Bedding Consumed (kg/day) 3.20 3.0
Total Roughage Intake (kg/day) 7.6 9.5
Weight Gain (kg/cow/day) .14 .65

Source: Ammoniation of Straw and Chaff, Kernan and Knipfel. Publication No.453, University of Saskatchewan.

The application of ammonia provides these advantages to producers:

  • increased forage digestibility by 10 to 15 percent
  • increased forage intake by 5 to 10 percent
  • increased crude protein content
  • prevents spoilage of high moisture forages

Steps in the Ammoniation Process


Consider the following points when choosing a location for ammoniating:

  • Make sure it is easily accessible to the anhydrous tank and other farm equipment.
  • Provide shelter to reduce wind damage to the plastic and weathering of the ammoniated forage.
  • Be sure the area is well-ventilated to reduce health hazards.
  • Locate the stack away from existing buildings. The combination of air and NH3 under certain extreme conditions, can be very explosive. Concentrations of 16 to 27 per cent ammonia in air often occur immediately following the addition of ammonia. When the concentration is in this range, temperatures of 5000 C (9320 F) or higher can cause ignition. Never smoke or light a flame near ammonia.
  • Place stacks 6 to 10 ft (2 to 3 m) apart to prevent ammonia from becoming trapped between them. This will further reduce the potential health hazards.


Stack the forage to fit the plastic available. Sheets of 6 mil black, polyethylene plastic are recommended for covering. During stacking, check the dimensions of the stack to ensure that the plastic sheet will cover the stack properly.

When covering of the stack is done carefully, only one sheet of plastic is required. If two sheets of plastic are used, never place a clear sheet over a black sheet as this produces a greenhouse effect and the plastic will melt.


The covered stack must be made as secure and airtight as possible. Holes which may have been produced during covering can be sealed with refrigeration or duct tape.

It is important that the plastic sheet be secured against the ballooning effect of the ammoniation process. Allow a minimum of 0.6 metres (2 ft) of plastic from the edge of the stacks to be weighted down. Sand bags can be used. A trench may also be dug around the stack and the plastic covered with the loose dirt.

It is advisable to place a belt of tape around the middle of the rectangular stacks to reduce wind damage. The plastic cover may also be secured from the wind with netting or twine.

High moisture stacks will settle resulting in loose plastic. This should be corrected seven to ten days after covering by loosening one side and tightening the plastic.


Iron pipes, 12 inches (4 cm) in diameter and approximately 22 feet (6.5 m) long, are used for ammoniation. The pipe is sealed to a closed, sharp point at one end and threaded at the other end. Holes, 3/16 inches (0.5 cm) in diameter, are drilled into the long pipe at 16 inches (0.4 m) intervals. A special adapter is used to attach the pipe to the ammonia source.  

The sharp point is needed to force the pipe through the stack, especially if round bales are used. The point of entry must be made airtight and this can be done in several ways. The loose plastic may be taped to the pipe at point of entry. A plastic sleeve may also be attached to the pipe at the point of entry and taped to the stack for an airtight seal.

The required amount of ammonia may be dispensed from either a truck or a tank on a trailer. Thirty minutes after the ammonia is added, the pipe may be capped and left in the stack, or removed and the hole resealed.

Caution! -- Tight fitting, unvented goggles and rubber gloves should be worn when working with anhydrous ammonia. An easily-opened container of water should be kept within easy reach to flush the gas from the face or skin if an accidental spill occurs. People should stand away from the stack during the ammoniation process to prevent possible contact with escaping ammonia gas.

The amount of ammonia applied is determined by the dry weight and type of forage. To accurately determine the amount of NH3 required, the moisture content of the forage must be known. It is also important to have available an estimate of the weight of the bales.

When being used to improve the protein content of low quality forages, ammonia should be added at 3 to 5 per cent of the dry matter weight. When ammonia is to be applied strictly as a preservative for high moisture hay, the level can be decreased to 2 per cent of forage dry weight.

Calculation Example

For this example the producer has 30 round bales of straw weighing 880 lb/bale (400 kg/bale). The moisture content of the bales is 15 per cent. The dry weight of the straw and the required amount of NH3 may be calculated in the following way:

Dry weight of forage

= No. of bales x Ave. bale wt. (kg) x (100 -- % moisture)

= 30 x 400 kg x 85

= 10,200 kg

Kilograms NH3 required

= Dry weight of forage (kg) x % NH3

= 10,200 kg x 3.5

= 357 kg

To convert kilograms to liters, a conversion factor of 6.4 lbs/gal (0.76 kilograms/liter) is often used. The exact density of the NH3 will, however, depend upon the ambient temperature.

Removal of Plastic Sheets

Stacks should remain covered for a minimum of three weeks. When removing the plastic sheets, remove the belt and tape prior to removing the sand bags. Pull the plastic off the stack into the wind. Choose a day when the wind is blowing away from the farm buildings. Fold the plastic sheets carefully as they can be reused. The ammoniated straw should remain covered until a few days before it is needed as feed and then used within four to five weeks to reduce nutrient losses from weathering and secondary fermentation. Ammoniated high moisture hay stacks should be of a size that can be fed out in approximately three to four weeks to reduce losses from secondary fermentations, especially if feeding during warm weather.

Feeding Ammoniated Forages to Livestock

Consider these points when feeding ammoniated forages to livestock:

  • Uncover stacks three to four days before feeding. This will allow excess ammonia to escape into the atmosphere.
  • Producer experience indicates that the palatability of ammoniated forages is excellent.
  • Ammoniated forage is a source of non-protein nitrogen (NPN). Avoid feeding it with other feedstuffs containing NPN.
  • Ammoniated crop residues and poor quality forages should only be used in well-balanced rations as determined by feed analysis.