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United States Department of Agriculture

Agricultural Research Service

Research Project: IMPROVING NUTRIENT DIGESTIBILITY TO ENHANCE FORAGE UTILIZATION IN LACTATING DAIRY COW FEEDING SYSTEMS Title: Evaluation of milk urea nitrogen as a management tool to reduce ammonia emissions from dairy farms

Authors
item POWELL, J MARK
item Wattiaux, M -
item Broderick, Glen

Submitted to: Journal of Dairy Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: June 23, 2011
Publication Date: September 1, 2011
Repository URL: http://handle.nal.usda.gov/10113/53871
Citation: Powell, J.M., Wattiaux, M.A., Broderick, G.A. 2011. Evaluation of milk urea nitrogen as a management tool to reduce ammonia emissions from dairy farms. Journal of Dairy Science. 94:4690-4694.

Interpretive Summary: Milk urea nitrogen (MUN) testing was developed to help dairy producers and nutritionists evaluate the protein levels and nitrogen use efficiency of dairy cattle diets. MUN levels greater than 14 mg/dL indicate that the animal is probably consuming nitrogen excessively, and excreting most of that nitrogen as urea in urine (UUN). Much of the UUN is converted to ammonia, an undesirable atmospheric emission. Since testing for MUN levels is already an industry-wide practice, we wanted to determine if it could also be a reliable indicator of ammonia emissions from dairy farms and therefore aid in policy development. In this study, we analyzed the results of six feeding trials to determine the relationships between feed nitrogen intake and UUN, and also between MUN and ammonia emissions. The analysis revealed that ammonia emission dropped between 10.3 and 33.7% when MUN levels decreased from 14 to 10 mg/dL. Wide-spread, effective use of MUN as a management tool to assess the impact of farm practices on ammonia emissions under a variety of commercial dairy farm conditions requires reliable and repeatable methods of both MUN and ammonia measurements. This study may help create new awareness, and perhaps industry-based incentives, for management practices that enhance feed nitrogen use efficiency and reduce MUN, UUN, and ammonia emissions from dairy farms.

Technical Abstract: The purpose of this study was to compile and evaluate relationships between feed nitrogen (N) intake, milk urea N (MUN), urinary urea N (UUN) and ammonia (NH3) emissions from dairy farms to aid policy development. Regression relationships between MUN (within the range of 10 to 25 mg/dL), UUN, and relative NH3 emissions were developed from studies conducted in Wisconsin, California, and The Netherlands. Relative reductions in NH3 emission were calculated as percent decreases in NH3 emissions associated with a baseline MUN level of 14 mg/dL (prevailing industry average). The two studies with cows in stanchion chambers provided relative linear reductions in NH3 emission of 14.1 to 25.6% when MUN levels decreased from 14 to 10 mg/dL. Similarly, analyses of 4 free-stall studies provided relative linear reductions in NH3 emissions of 10.3 to 33.7% when MUN levels declined from 14 to 10 mg/dl. Wide-spread, effective use of MUN as a management tool to assess the impact of farm practices on NH3 emissions under a variety of commercial dairy farm conditions requires reliable and repeatable methods of both MUN and NH3 measurements. This study may help create new awareness, and perhaps industry-based incentives, for management practices that enhance feed N use efficiency and reduce MUN, UUN and NH3 emissions from dairy farms.

Last Modified: 9/10/2014
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