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ARS Home » Midwest Area » Madison, Wisconsin » U.S. Dairy Forage Research Center » Dairy Forage Research » Research » Publications at this Location » Publication #319834
Title: Milk urea nitrogen (MUN) tool reduces nitrogen emissions from dairy farms

Author
item Powell, Joseph

Submitted to: Global Research Alliance on Agricultural Greenhouse Gases - Livestock Research Group Newsletter
Publication Type: Popular Publication
Publication Acceptance Date: 8/20/2015
Publication Date: 2/9/2016
Citation: Powell, J.M. 2016. Milk urea nitrogen (MUN) tool reduces nitrogen emissions from dairy farms. Global Research Alliance on Agricultural Greenhouse Gases - Livestock Research Group Newsletter. Available: http://globalresearchalliance.org/research/livestock/.

Interpretive Summary:

Technical Abstract: The milk urea nitrogen (MUN) tool was developed to monitor dietary crude protein (CP) use and feed costs. MUN within the range of 12 to 10 mg/100 ml milk usually indicates the recommended dietary CP level of 16.5%. MUN levels greater than 12 mg/100 ml indicate dietary CP is being wasted and excreted as urinary urea nitrogen (UUN). Ammonia emissions from UUN account for 60 to 70% of total nitrogen (N) loss from dairy farms. Some emitted ammonia re-enters the terrestrial N cycle to become an indirect source of nitrous oxide, the most potent agricultural greenhouse gas. Each unit reduction in MUN indicates UUN reduction of 16.6 g/cow per day and UUN intensity reduction of 446 mg UUN/kg milk. Simulations using Wisconsin on-farm MUN data revealed that on a state-wide basis, improved dietary CP feeding guided by the MUN tool would reduce ammonia emissions by 29% to 43% and nitrous oxide emissions by 15% to 22%. More precise feeding using MUN would provide multiple pathways to climate change adaptation and mitigation. On most dairy farms more precise feeding would provide savings, and therefore create opportunities to invest in technologies such as more comfortable animal housing and manure storage modifications, which would reduce the effects of forecasted increases in temperature and fewer but heavier rainfall events. To accommodate for intrinsic variation in MUN associated with production systems or animal genetics, baseline and subsequent target MUN values may need to be established on a per herd basis. Other requirements include accurate and reliable MUN assays, and collaboration among producers, nutrition consultants, milk processors, and policy makers to establish MUN benchmarks and targets. Economic incentives such as price premiums for milk shipped within a desired range of MUN may nudge the dairy industry toward a decrease in undesirable N emissions.