Strategies For Reducing Ammonia Emissions
Posted: April 10, 2004
Producers are currently addressing phosphorus and water quality concerns. Now the agricultural industry is being asked to evaluate air quality, especially ammonia emissions. The science to monitor and regulate ammonia and nitrogen is not as clear-cut as phosphorus. However, there are nutritional strategies and management practices that can be implemented to reduce nitrogen excesses.
The same basic approach to solving the phosphorus (P) problem can also be used to control nitrogen (N); reduce purchased nutrients onto the farm and reduce the dietary levels. For ruminants, the emphasis is on feeding management practices followed by ration formulations as the most effective means to reduce ammonia emissions. In addition, managing ammonia emissions requires consideration of factors that affect the rate of ammonia production: production stages of animals, temperature, humidity, pH, ventilation, and manure storage systems.
Animal nutritionists can estimate the N in manure and its availability for volatilization as ammonia. For ruminants, this is based on an understanding of nitrogen metabolism. Urinary urea-N is formed when the products of the microbial degradation of dietary crude protein in the rumen are not incorporated into microbial protein but absorbed, ultimately causing an elevation in blood or milk urea nitrogen. The high concentration of urea in urine and the high urease activity of feces indicate that the breakdown of urea in manure will be an important source of ammonia. There is scientific evidence to demonstrate that N excretion, particularly as urea-N in the urine, can be altered through dietary manipulation of protein and carbohydrates.
Ruminant protein nutrition is complicated and does involve more than lowering the dietary crude protein level to reduce ammonia emissions. Balancing protein, protein fractions and carbohydrates will be integral to controlling ammonia emissions as well as maintaining animal performance. For ruminants, forage quality can dramatically alter the feasibility of controlling ammonia emissions. Herds feeding high levels of alfalfa silage are limited in the strategies they can implement to control protein levels in the diet. While high producing dairy cows can be successfully fed crude protein levels at 16% in the total ration, it is nearly impossible to achieve these low levels and balance amino acids when high protein haycrop forages make up the majority forage. In order for producers to comply with future policies on ammonia levels, a change to cropping systems may be required.
Feeding management practices taught over the years are more important then ever in order to comply with changing environmental policies. Pennsylvania has over 9,000 dairy farms, which equates to 9,000 different scenarios related to forage, forage quality, and concentrate ingredients. This requires producers and managers to focus on frequent dry matter testing on all high moisture feeds, routine forage and feed analyses and monitoring dry matter intakes, to name a few. Attention to nutrient levels in all animal groups will be important as this global issue of ammonia, comes to the forefront of concerns.
There are many questions and unknowns related to ammonia emissions. However, there are current practices available to all livestock producers that can help improve on farm nutrient efficiencies, minimize excess nutrient feeding, and reduce nutrient excretions such as N and P.
Virginia A. Ishler, Extension Associate, Penn State Dairy Alliance, Nutrient Management & PSU Dairy Unit Manager