Improving the efficiency of nitrogen use and reducing ammonia emissions from Pennsylvania dairies

Improving the efficiency of nitrogen use and reducing ammonia emissions from Pennsylvania dairies

Summary

Twelve dairies in Central, Southeast, and Southwest Pennsylvania participated in the demonstration phase of this project. Ammonia emissions off the barn floor and in controlled laboratory environment, milk production, milk composition, and income-over-feed costs were monitored before and after a 1%-unit reduction in dietary protein. The reduction dietary protein resulted in a 23% reduction in the ammonia emitting potential of manure. Flush dairies emitted less ammonia from the barn floor than scrape or gravity-flow dairies. Average milk urea nitrogen concentration tended to be reduced and income-over-feed-costs was increased by $0.62/cwt for the low-protein feeding periods. There was no difference in milk yield or milk fat and protein contents of bulk tank milk samples between the high- and low-protein feeding periods. Data from the demonstration stage of the project were summarized in a newsletter distributed to more than 3,500 Pennsylvania recipients (producers and dairy-related businesses; see attachment). Summarized data from the project were presented to a total of 291 dairy nutritionists and professionals at the 2011 Penn State Dairy Cattle Nutrition Workshop. Results from the project were also presented at the 2011 PA Agronomic Education Conference, the Midwestern section meeting of the American Society of Animal Science, the national meeting of the American Dairy Science Association, and to 57 dairy producers at the 2012 Southwest PA Regional Dairy Day (two locations). An article highlighting the project was published in the March’12 issue of Farmshine, the premier farm publication in the Northeast.

Objectives/Performance Targets

Reduce whole-farm nitrogen inputs on 50 Pennsylvania dairies, representing 5,000 cows and 10,000 acres by approximately 150 tons/yr and reduce ammonia emissions from these dairies by 50 tons/yr while maintaining or improving profitability as measured through income-over-feed-cost.

Accomplishments/Milestones

Twelve small (50 cows) to larger (550 cows) free- or tie-stall dairies in Central, Southeast, and Southwest Pennsylvania with scrape, gravity-flow, or flush manure management systems participated in the demonstration phase of this project. A total of four sampling events were conducted, including two baseline sampling periods (fall 2009 and spring 2010) during which the dairies were feeding their ‘control’, i.e. high-protein diets and two low-protein feeding periods (fall 2010 and spring 2011). Extensive forage and diet sampling was carried throughout the project to verify dietary crude protein levels. Following consultations with the dairymen and their nutritionists, a 1%-unit drop in dietary protein (from 16.5 to 15.3%) was achieved in most participating dairies in the 2nd year of the project. Barn floor and laboratory ammonia emissions, i.e. ammonia emitting potential of manure (AEP), were measured before and after the dietary protein reduction. Data for milk yield, milk composition (including milk urea nitrogen), and income-over-feed-cost were also collected throughout the project. Barn floor measurements showed that ammonia emissions were drastically lower during the low-protein periods compared with the high-protein periods (186 vs. 445 mg/m2/h). These results, however, were confounded by lower ambient temperature during the low-protein periods (43.5 vs. 56.3?F, respectively). The AEP of manure, which was based on evaluation of reconstituted (urine and feces) manure at the same temperature, was on average 23% lower for the low-protein vs. high-protein feeding periods (292 vs. 378 mg/m2/h). We also measured manure emissions of methane, nitrous oxide, and carbon dioxide, which are important greenhouse gases. Emissions of methane and carbon dioxide were not affected by dietary changes and emissions of nitrous oxide from stored manure were negligible. Barn floor ammonia emissions were lower for flush vs. scrape and gravity-flow manure management systems. The greatest methane emissions were observed for the gravity-flow manure system. Milk yield (71.0 vs. 71.5 lbs/d, high- and low-protein periods, respectively) and milk fat and protein contents were not different between the low- and high-protein feeding periods. Concentration of milk urea nitrogen tended to be lower during the low-protein periods (13.2 vs. 14.5 mg/dL, respectively) and income-over-feed-costs increased by $0.62/cwt for the low-protein feeding periods. Overall, our conclusions from this project were that manure ammonia emissions can be significantly reduced by moderately decreasing dietary protein content without affecting milk yield and composition and increasing farm profitability by increasing income-over-feed-costs. Data from the demonstration stage of the project were summarized in a newsletter distributed to more than 3,500 Pennsylvania recipients (producers and dairy-related businesses; see attached newsletter). Summarized data from the project were presented to dairy producers and industry professionals at various regional and national meetings. Results from the project were presented to a total of 291 dairy nutritionists and industry professionals at the 2011 Penn State Dairy Cattle Nutrition Workshop held Nov 9-10th at the Holiday Inn, Grantville, PA, at the 2011 PA Agronomic Education Conference (State College, PA), the Midwestern section meeting of the American Society of Animal Science (Des Moines, IA), the national meeting of the American Dairy Science Association (New Orleans, LA), and to 57 dairy producers at the 2012 Southwest PA Regional Dairy Day (two locations at Greensburg and Bedford, PA; see attached brochure). An article highlighting the project was published in the March’12 issue of Farmshine, the premier farm publication in the Northeast (article is attached).

• Project Newsletter
• SW PA Dairy day
• Farmshine-March’12

Impacts and Contributions/Outcomes

Project activities planned for the reporting period have been completed. Farm milk production, composition, income-over-feed-costs, and ammonia emissions data were collected during eight sampling events. Reduction of dietary crude protein by about 1%-unit resulted in at least 23% reduction in ammonia emissions from manure, did not affect milk yield, and increased income-over-feed cost by $0.62/d in commercial Pennsylvania dairies. Data from the demonstration stage of the project were summarized in a newsletter distributed to more than 3,500 Pennsylvania recipients (producers and dairy-related businesses) and presented to a total of 291 dairy nutritionists and professionals at the 2011 Penn State Dairy Cattle Nutrition Workshop, to 57 dairy producers at the 2012 Southwest PA Regional Dairy Day, and at various regional and national professional meetings.

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