True Value in Ammoniating Straw

By Murray Feist, Provincial Livestock Specialist, Saskatoon

A shortage of forage for feed often results in producers looking to incorporate straw based rations for their livestock. Anhydrous ammonia has been used as a treatment to improve energy and protein levels in straw. Anhydrous ammonia (NH₃) increases the free nitrogen in the straw, therefore improving protein content, digestibility and energy availability. Crude protein improvement can be achieved between 85 and 125 per cent from base levels and energy, or total digestible nutrients, (TDN) up to 10 to 15 per cent. Total dietary intake of treated straw may increase by five to 10 per cent compared to untreated straw. Anhydrous ammonia is most effective when applied to straw that contains less than six per cent protein and 48 per cent TDN. The increase in protein and digestible energy may allow producers more flexibility when formulating their rations and assist with managing their feed supply and feeding programs.

Cost of Treatment

Table 1 shows some standard nutrient values (per cent dry matter basis) for a grass hay, straw and anhydrous ammonia treated straw. It shows that treatment with anhydrous ammonia will increase protein, energy and digestibility of straw.

Table 1. Feed nutrient values (percent dry matter).

The following example shows that if using a current market price for anhydrous ammonia of $1,050 per tonne, an application rate of 3.5 per cent to the dry matter weight of the straw would cost $30.50 per fed tonne plus an additional $27.55 per tonne for silage plastic as a cover. Note that these costs do not include the cost of protective equipment or labour involved.

Example 1. 25 Straw Bales weighing 800 lbs., 17 per cent moisture (83 per cent dry matter) and 3.5 per cent anhydrous ammonia application rate.

• Stack Dry Matter Content:
  • 25 bales x 800 lbs. per bale x 83 per cent dry matter = 20,000 lbs. x 83 per cent = 16,600 lbs. dry matter.
• Weight of Anhydrous Ammonia Required:
  • 16,600 lbs. straw dry matter x 3.5 per cent anhydrous ammonia = 581 lbs.
  • 581 lbs. anhydrous ammonia ÷ 16,600 lbs. straw dry matter = 0.035 lbs. anhydrous ammonia per pound straw dry matter
• Cost of Application:
  • $1,050 per tonne anhydrous ammonia = $0.48 per pound anhydrous ammonia
  • 581 lbs. x $0.48 per pound = $276
  • $276 ÷ 20,000 lbs. (as fed) = $0.0138 per pound straw = $30.42 per tonne
  • 800 lbs. bale x $0.0138 per pound ammoniated straw = $11.04 per bale
• Covering Costs:
  • Silage plastic (40x100 feet, six mil., black polyethylene) = 4,000 square feet
  • $0.0625 per square foot x 4,000 square feet = $250
  • $250 ÷ 20,000 lbs. straw = $0.0125 per pound = $27.55 per tonne
  • $0.0125 x 800 lbs. straw bale = $10 per bale

Final Cost (minus labour, equipment and personal protective equipment):

• Anhydrous treatment cost: $30.42 per tonne
• Covering cost: $27.55 per tonne;
• Total cost (minus labour and application of equipment): $57.97 per tonne;
• Base straw value: $100 per tonne; and
• Ammoniated straw final value (minus labour and application equipment): $157.97 per tonne.

Table 2 shows three sample rations comparing a hay, straw ration and ammoniated straw ration. All diets are formulated to sustain a 1,450 beef cow in early gestation, under ambient temperatures and targeting a 0.50 lbs. per day daily gain. (Note: to simplify the calculations, no labour or mineral/vitamin supplementation costs were included).

Feeding a straw based ration is the most cost effective at $2.29 per head per day, followed by the hay ration at $2.31 and ammoniated straw ration at $2.55 per head per day. The treatment of straw with anhydrous ammonia resulted in an increased daily feeding cost by 11.5 per cent over untreated straw with marginal increases in forage intake and estimated daily gain performance. Improvements in straw crude protein, TDN content and forage intake came at an additional cost of $57.97 per tonne thus resulting in a higher ration cost relative to untreated straw or base hay rations.

Table 2. Sample ration costs comparing hay, straw and ammoniated straw diets for a 1,450-lb. dry cow in early gestation, 0.50 lbs. per day average daily gain.

Assumed Costs: Brome Hay: $220/tonne. Barley Straw: $100/tonne. Ammoniated Barley Straw: $157.97/tonne. Barley grain: $356/tonne. Vitamins and Minerals are not included. A properly formulated diet should be based on recommendations from a livestock nutritionist or specialist.

Finally, Table 3 shows a comparison value by percent unit of crude protein and TDN (dry matter basis) for the hay, straw and ammoniated straw. In this example, ammoniated barley straw not only provides a higher protein feed, but also a more affordable protein relative to the price of untreated straw. However, this example also illustrates that by increasing the available TDN in the treated straw by 15 per cent (42 to 48 per cent) is offset as the TDN is now 38 per cent more expensive per unit of TDN ($3.29 vs $2.38) due to the treatment cost of $57.97 per tonne straw. The true value in treating straw with anhydrous ammonia is illustrated by an increase in crude protein content (4.2 to 8.5 per cent) relative to the cost of treatment and a cheaper protein value from $23.81 to $18.58 per unit crude protein.

Table 3. Per unit value of crude protein and energy (TDN) for hay, straw and ammoniated straw*

*Price per unit of crude protein or per unit of TDN is calculated by dividing the $/tonne by the nutrient unit. Brome Hay: $220/tonne ÷ 10.6 per cent crude protein = $20.75/per cent crude protein.

Summary

When treating straw and chaff with anhydrous ammonia, a cost: benefit analysis needs to be considered, particularly with increased financial costs associated with the covering and application of anhydrous ammonia. Ammoniating straw provides a valuable increase in protein, enhances energy levels and increases the amount of straw that may be utilized in rations. This benefit would allow a producer to be flexible in stretching scarce feed resources even further.

For more information on applying anhydrous ammonia, contact the Agriculture Knowledge Centre at 1‑866‑457‑2377.