Ammoniation of Low Quality Forages: An Old Practice With New Relevance?


In 1964, Bob Dylan released his popular song and album “The Times They Are a-Changin.” Although this song was recorded 56 years ago, it is regarded by many as one of the most highly influential songs in American history and it seems quite fitting to reference it here for this discussion. The underlying message of Dylan’s work is one of continual, lasting change, and we would all agree that our lives and industry have certainly changed over the last few months.

At the time of this writing (April 2020), ethanol production has sharply decreased for numerous reasons causing widespread shortages of corn milling by-products which have otherwise been a relatively abundant staple in rations for many years. How exactly this plays out in the coming months remains to be seen, but if this is the new “normal,” then our approach to protein and energy nutrition in beef cattle diets will need to be re-thought as we move forward. Forage quality and the role it plays on energy and protein intake is paramount in forage-based diets. Treatment of low-quality forages with anhydrous ammonia is one technique that may have more applicability if by-products are limited, and the goal of this discussion is to review this method as a practical alternative for use in forage-based diets.

The process of chemical treatment of low-quality forages is well established with much of the original research in this area conducted in the 1970s and 80s. Our goal is that ammonia and water react to break the bonds of the fiber components, resulting in a forage that is more digestible and ultimately contributing to an increase in intake and energy available to the animal. Ammonia applied will remain attached to the forage so samples tested will also show an increase in crude proteincontent. If forage intake increases, then the result is an increase in total protein intake, although primarily from non-protein nitrogen.

This method works best on any forages that are ≤5-6% crude protein and ≤50% TDN. Forages with higher protein and lower fiber components will respond less to ammoniation, so there is little to gain nutritionally by ammoniating a forage that is already higher priced to begin with. There is also greater risk of toxicity and other associated symptoms (circling, incoordination, convulsions) with ammoniating higher quality forages, so we only recommend this method on poorer quality feedstuffs. Changes in forage digestibility, crude protein, and intake due to ammoniation across multiple study locations and forage types are summarized in Table 1.

Regarding cattle performance, most studies show an improvement due to ammoniation but the response will vary depending on the level of treated forage fed in the diet, inclusion of other protein and energy sources, and type and weight of cattle being fed. Researchers at the University of Florida (Brown et al., 1987) found that fiber (NDF and ADF) digestibility increased as the level of ammonia applied to low-quality tropical hay increased from 0 to 4% of dry matter. They also observed an increase in both intake and gain for steers fed ammoniated rice straw compared to feeding non-ammoniated straw plus urea.

When anhydrous ammonia was applied at 5% of dry matter to wheat straw, dry matter intake of steers increased in work done in Oregon (Herrera-Saldana et al., 1982). Data from Kansas State University (Fike et al., 1995), suggests that while ammoniated wheat straw by itself may be sufficient for maintaining weight and body condition of gestating cows, additional protein and/or energy supplementation may be necessary to result in significant positive changes in cow weight and condition. A more recent study in Nebraska (Conway et al., 2018, Table 2) showed that intake, gain, and feed conversion all improved due to ammoniation when 700 lb steers were fed corn stover at 65% of the diet with 30% wet distillers grains (dry matter basis).

While generally a simple task to complete, applying anhydrous ammonia to forages does require a little planning and forethought. Round bales should be stacked in a pyramid shape and large square bales stacked in a rectangular shape, ideally allowing some room between rows of bales because we want to maximize the surface area of the bale that is exposed to ammonia. We want to create an air-tight environment, so the stacks must be completely covered with plastic and sealed to contain the ammonia within the forage. Around the base of the stack, use soil to cover the edge of the plastic to hold it in place and prevent ammonia from escaping. Most recommendations are to apply ammonia at a rate of 3% or 60 lb per ton of forage dry matter, so you need to know the total tonnage of forage you are working with and the moisture content. The moisture content of forage is important, not only to determine the amount of anhydrous to apply, but also because the process is moisture dependent and digestibility usually improves to a greater extent with forages carrying more inherent moisture. Ambient air temperature affects how long the ammoniation process takes to complete. Often done during summer after wheat harvest when new crop straw is available, ammoniation at that time of the year when temperatures are higher will require less time for the forage to be sealed. We can ammoniate forages such as corn stalks later in the fall when it is cooler, but we may need to keep the stack sealed for 30 days or longer for it to be effective.

Anhydrous ammonia is currently about $500/ton, so applying at 3% would result in an ammoniation cost of $15/ton of forage dry matter for just the anhydrous applied. You will need to add the cost of plastic, labor and any other costs to fairly determine the final cost to ammoniate. Please remember that anhydrous ammonia can cause irritation and burning to the skin, eyes, and mouth, not to mention that it is a highly explosive gas maintained under pressure. We cannot stress enough the importance of safety with this process and using common-sense and good judgment. Wear protective equipment, check hoses and valves, as well as the plastic covering the treated forage for leaks, be aware of wind direction, and make sure children don’t play around treated stacks. If done properly and safely this method is effective and has been for many years. We hope this article finds everyone well and safe during these trying times, and please feel free
to contact us for more details if you would like to discuss how this could fit into your current program.

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