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How much ammonia is your litter producing? Wide variations are found between flocks in how much ammonia is released every hour from the litter. In ten week old turkey flocks, moist, composted litter can produce 300 times as much ammonia each hour as dry litter with ample fresh straw added. If the ammonia level in the air exceeds 10 ppm, the turkey’s ability to fight respiratory disease is impaired. Even when the ventilation system is able to keep ammonia levels in the air low, litter which produces high levels of ammonia tends to increase breast blisters due to irritation of the bird’s skin when it sits on the litter. It is important to be able to control both ammonia production and air ammonia levels in your barn to help maintain bird health and carcass quality.
Strategies for managing ammonia production in your barn:
The bacteria in turkey litter need a supply of carbon and nitrogen before they can grow and produce ammonia in your barn. As the flock grows older, the manure builds up and the straw breaks down, providing ready sources of these nutrients. If you compost or re-use litter, the ammonia-producing bacteria will multiply at a much earlier age in the flock because the old litter already contains a large supply of available nitrogen and carbon. Higher bird density will also encourage ammonia production as the manure builds up more quickly.
A minimum level of moisture, approximately 30%, is required to support growth of the ammonia-producing bacteria and this growth will accelerate as moisture levels increase from 30% to 40%. In practice, it is very difficult to keep moisture levels below 30% throughout the life of the flock without incurring high ventilation and heating costs or using very low bird densities. Even if you do manage to keep the litter dry, dust levels will increase and cause the airsac damage that you are trying to avoid by controlling ammonia levels. In practice, it should be possible to keep litter moisture in the 30 to 35% range at any location in the barn that is 1.0 m or more away from a drinker. Litter in that moisture range will not be wet but will still stick together if you squeeze it in your hand.
While the role of moisture in increasing ammonia production is well known, its ability to trap ammonia should not be overlooked. Significant quantities of the ammonia produced in the litter become dissolved into the litter moisture, preventing the ammonia from being released as a gas into the air. Litter treatments which acidify or lower the litter pH will increase the amount of ammonia trapped in the litter moisture. The ammonia holding capacity of the litter will provide a temporary buffer against increased ammonia production.
If the litter starts to dry, ammonia trapped in the moisture will be freed as a gas into the air and ammonia will build up in the barn if ventilation rates are not increased. Roto-tilling or turning the litter will also increase ammonia release by exposing the wet, ammonia saturated litter to the air. The litter may need to be tilled twice a week to avoid releasing large quantities of ammonia each time the litter is turned.
The litter in the “donut” or “ring” around the drinker contains 60 to 75% moisture, a level which traps most of the ammonia produced and reduces the activity of the bacteria. The crust which forms on top of the drinker ring also acts as a physical barrier to ammonia release. At a distance of 0.3 to 1.0 m from the drinker ring, ammonia release increases because the moisture level in the litter is high enough to support rapid growth of ammonia-producing bacteria but not high enough to trap all of the gas produced. Producers who move their drinkers on a regular basis to prevent rings from forming will not decrease ammonia production because they are simply redistributing the moisture around a wider area of the barn. Drinker management, which decreases total water spillage, will reduce the total amount of moisture in the barn and lower ammonia production in the litter.
Adding fresh litter has an immediate effect on ammonia production because it forms a dry, physical barrier which prevents ammonia release into the air. If new straw is added on a regular basis, ammonia production will be further reduced because the litter will stay drier and the available carbon in the litter will be reduced. The fresh straw has a larger particle size and bacteria have more difficulty extracting carbon from it than the smaller, broken down particles in old litter. A deeper litter base will also encourage water to drain away from the litter surface and help keep the ammonia trapped in the litter pack. Barns where the litter is 10 cm deep or deeper tend to have less ammonia production because of the cumulative effect of the litter addition.
Dropping the barn air temperature below 18C will cause a noticeable decline in the growth of ammonia-producing bacteria and this decline will continue if temperature is reduced even more. To crudely gauge ammonia production in the litter and to find “hot spots” in the barn, you can measure the temperature 1 cm below the litter surface. After 6 weeks of age, litter that is 27C or higher will likely be producing high levels of ammonia. In a cool barn, (e.g. 15C), the litter will likely be cooler than 27C but any areas where the litter is 5C warmer than the barn air will still be producing significant levels of ammonia. The litter is usually warmer than the barn air because of the heat produced by the litter bacteria.