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

Final Report for LNE09-286

Project Type: Research and Education
Funds awarded in 2009: $179,940.00
Projected End Date: 12/31/2012
Region: Northeast
State: Pennsylvania
Project Leader:
Dr. Alexander Hristov
Pennsylvania State University
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Project Information

Summary:

Twelve small (40 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).

Diet composition was monitored for at least 2 weeks before sampling and data collection. Average crude protein concentration of the diets during the low-protein feeding periods was 15.4%, which was within our target of 1%-unit reduction (compared with the high-protein feeding period, average of 16.5%). Ammonia emissions off the barn floor and in controlled laboratory environment (i.e., ammonia emitting potential of manure, or AEP) were measured twice during each sampling period.

Bulk tank milk production, milk composition, and income-over-feed costs were also monitored before and after the reduction in dietary protein. Barn floor ammonia emissions were lower during the low-protein periods but the effect of dietary protein reduction was confounded with lower ambient and manure temperatures.

The AEP of manure, which directly reflects dietary changes and manure composition, was reduced on average by 23% for the low-protein feeding periods. Flush dairies emitted less ammonia from the barn floor than scrape or gravity-flow dairies. The greatest methane emissions were recorded for the gravity-flow manure systems. Average milk urea nitrogen concentration also tended to be reduced and income-over-feed-costs was increased by $0.62/cow/d 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.

Whole-farm nitrogen input was reduced by about 5,100 lbs per farm per year on 12 Pennsylvania dairy farms, totaling 1,880 cows and 6,900 acres. Total feed nitrogen input in these farms was reduced by 31 tons per year, and total ammonia emissions were reduced by an estimated 33 tons per year. These reductions had no effect on milk production, and farm profitability (as income-over-feed-costs) increased by $0.62 per cow per day.

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 2011 Midwestern section meeting of the American Society of Animal Science, the 2012 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. A full-length manuscript is in preparation for submission to the Journal of Dairy Science.

A survey of 59 dairy nutritionists in the Northeast indicated that the most probable cause for not implementing low-protein feeding strategies was concern for reduced production. This outcome clearly demonstrates the need to further propagate among nutritionists and dairy producers the benefits of low-protein diets and lack of negative effects on productivity when the diet is properly formulated. An important part of this process should be the involvement of Plain community dairy farmers.

Introduction:

The dairy cow is a relatively inefficient utilizer of dietary protein and on average only 25% of the ingested protein is secreted with milk and the remaining 75% are lost with feces and urine. On contact with feces, urinary urea is rapidly hydrolyzed to form ammonia. At the pH commonly found in manure, ammonia rapidly volatilizes: up to 40% of the nitrogen in dairy manure can be lost in 24 hours after excretion.

Ammonia volatilization from animal manure is a critical issue in today’s production animal agriculture because farm animals are considered the greatest contributor to gaseous ammonia emissions in the U.S. (50% of the emissions; National Research Council data) and ammonia is hazardous to human health, represents a loss of fertilizer value, and can adversely impact the environment, contributing to eutrophication, soil acidity, aerosol formation, and impaired visibility. As a result, the U.S. Environmental Protection Agency (USEPA) ruled on January 20, 2009 that animal feeding operations (AFO) that did not endorse the 2005 USEPA Air Quality Compliance Agreement must notify emergency response officials if they emit 45 kg or more of ammonia or hydrogen sulfide in a 24-hour period. Thus it becomes critical for the animal industries to understand the factors controlling ammonia emission from manure and make every effort to reduce these emissions from animal operations.

The process of ammonia formation and volatilization from animal manure is almost instantaneous and begins immediately after urine and feces are excreted. Once emitted, ammonia enters rapidly into simple chemical reactions primarily with sulfur and nitrogen oxides. The dynamics of these reactions, however, are very complex and depend on environmental conditions and concentration of reactants. In general, ammonia is present in the troposphere in very low concentrations, ranging from 1 to 25 ppb. Due to its high reactivity, ammonia reacts with sulfuric and nitric acids forming ammonium sulfate, ammonium bisulfate or ammonium nitrate, considered PM2.5 (particles with aerodynamic diameter less than or equal to 2.5 µm; sometimes referred to as “fine particles”; USEPA). These particles contribute to air pollution, which globally is estimated to cause up to 2 million premature deaths annually [World Health Organization (WHO) data]. Of the pollutants monitored by the WHO, particulate matter affects more people than any other air pollutant. Even low concentrations of air pollutants have been related to a range of adverse health effects. Fine particulate matter (PM2.5) is considered among the most dangerous as when inhaled it may reach the peripheral regions of the bronchioles and interfere with gas exchange inside the lungs (WHO).

On a dairy operation, ammonia can be emitted from housing, manure storage, and manure application. Minimizing nitrogen excretion, which can be achieved through dietary-modifications, is naturally the first line of defense in curbing ammonia emissions from livestock operations. Available research data indicate that diets fed to animals have profound effects on ammonia emissions from excreted manure. Overfeeding dietary protein, imbalanced amino acid supply, and/or reduced energy availability for ruminal fermentation in ruminants result in increased urinary and fecal N losses and consequently increased ammonia emissions from manure. Data from Penn State have demonstrated a direct relationship between the amount of protein fed to lactating dairy cows and the ammonia emitting potential of manure. As a result, reducing dietary protein concentration can have a dramatic effect on ammonia losses from dairy manure.

Crude protein is routinely overfed to dairy cows in the U.S. and levels of around 17-17.5% are common for dairy operations across the country. The main reason for these practices is the belief that increasing dietary protein leads to increased milk yield. Controlled experimental data and large meta-analyses, however, have clearly demonstrated that increased dietary protein only marginally increases milk yield but drastically reduces milk nitrogen efficiency as most of the intake protein is lost with urine and feces and a significant proportion is eventually volatilized as ammonia. Based on a dataset of more than 1,700 diets, we estimated that for every 1%-unit increase in dietary protein, there is approximately 36 g/d N lost with feces and urine and only 3 g/d increase in milk N output.

Performance Target:

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.

Whole-farm nitrogen input was reduced by about 5,100 lbs/farm/year in 12 Pennsylvania dairy farms totaling 1,880 cows and 6,900 acres. Total feed nitrogen input in these farms was reduced by 31 tons/yr and total ammonia emissions were reduced by an estimated 33 tons/yr. These reductions had no effect on milk production and farm profitability (as income-over-feed-costs) increased by $0.62/cow/d.

Cooperators

Click linked name(s) to expand
  • Dr. Sarah Dinh
  • Dr. Ken Griswold
  • Virginia Ishler
  • Dr. Gene Schurman
  • Dr. Eileen Wheeler

Research

Materials and methods:

Twelve small (40 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 were recruited to participate in the project (see Table 1 in appendix for farm details). 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 (see Table 2 dietary protein levels and an example of a dietary change). 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.

Since ammonia emissions were a key measurement in this project, details on the data collection procedure are provided here. In the barn, manured- surface ammonia emissions were determined using a non-steady state, internal air recirculating, flux chamber. Flux chamber internal gas concentrations were measured using a model 1412 photoacoustic field gas monitor, (INNOVA, model 1412). Eight farms (two farms per each of four manure handling system) were measured using the flux chamber method. Each of these farms was measured twice in the fall and twice in the spring. When the low-protein feeding was established (Year 2), this measurement cycle was repeated. Manure samples (feces and urine) were collected from all farms, twice in the fall and twice in the spring. These manure samples were analyzed in the lab for 24-h AEP using a steady state flux chamber. The controlled environment of the steady state flux chamber system controls the airflow rate, temperature, and feces:urine ratio of the samples. Gas samples from all farms were analyzed for ammonia, nitrous oxide, methane, and carbon dioxide. Ambient air temperature and relative humidity were monitored whenever emission measurements were being collected via electronic data-loggers (Onset Hobos). Manure surface temperature was measured with hand-held infrared temperature instrument.

Research results and discussion:

Milestone 1: Nine Pennsylvania dairies representing all management styles serve as demonstration sites by reducing N inputs by approximately 6,000 lbs/yr/dairy, increasing the efficiency of conversion of feed nitrogen into milk protein by 13%, and decreasing ammonia emissions by approximately 2,000 lbs/yr/dairy (a 20-25% reduction).

Twelve Pennsylvania dairies were recruited and participated as demonstration sites for the project. By reducing dietary protein, the whole-farm nitrogen input in the demonstration farms was reduced by about 5,100 lbs/farm/year. Milk nitrogen efficiency on these farms was increased by 8% (from 25.6 to 27.7%). A minimum of 23% reduction in ammonia emissions from manure was achieved (see Results below).

Milestone 2: 400 Pennsylvania dairy producers are educated on feeding strategies to reduce ammonia emissions, while maintaining or improving income over feed costs and improving air quality by managing a low-nitrogen input dairy operation.

Data from the demonstration stage of the project were summarized in a newsletter distributed to more than 3,500 Pennsylvania dairy producers and dairy industry professionals.

Milestone 3: 50 Pennsylvania dairy producers adopt low N input strategies. Whole-farm nitrogen inputs from feed sources and ammonia emissions from manure on these dairies are reduced by approximately 150 and 50 tons/yr, respectively.

Twelve dairy producers were directly involved in the project and continued feeding reduced protein diets after the expiration of the project. Results from the project were disseminated to more than 3,500 Pennsylvania dairy producers and industry professionals but cannot verify how many dairy farms have adopted low-protein feeding. Our observation is that this practice becomes increasingly popular among dairymen and their consulting nutritionists.

Milestone 4: Through popular press articles, newsletters, and other extension publications disseminate results from the project to over 3,000 dairy producers in the state.

Data from the demonstration stage of the project were summarized in a newsletter distributed to more than 3,500 Pennsylvania dairy producers and dairy industry professionals.

Results and Discussion: As shown in Table 2, the dietary manipulation was successful and average dietary protein decreased by about 1%-unit from the high- to low-protein periods of 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; Table 3). These results, however, were confounded by lower ambient temperature during the low-protein periods (6.4 vs. 13.6ºC, respectively), which resulted in about 5ºC difference in manure temperature. Temperature is a critical component of the ammonia volatilization process and difference in air or manure temperatures are certainly affecting gaseous emissions.

The ammonia-emitting potential (AEP) test developed in our laboratory is designed to eliminate the environmental effects on ammonia emissions from manure. The test is based on evaluation of ammonia emissions from reconstituted (urine and feces) manure at the same temperature. As shown in Table 3, the AEP of manure was on average 23% lower for the low-protein vs. high-protein feeding periods (291 vs. 378 mg/m2/h). We also measured 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. Nitrous oxide emission involves an aerobic process and emissions from stored manure are negligible or none.

Barn floor ammonia emissions were considerably lower for flush vs. scrape and gravity-flow manure management systems (Table 4). The lowest methane emissions were observed for the flush system and the greatest for the gravity-flow manure system. There was a significant interaction between diet and manure system, which reflected the significantly greater methane emissions from gravity-flow manure systems with the high-protein, but not the low-protein diets. Emissions of carbon dioxide were not different due to the manure system. Nitrous oxide emissions were negligible and there was a trend for lower emissions with the flush systems. An important factor that needs to be kept in mind was the considerably higher manure temperature (and thickness) with the gutter-scrape and gravity-flow vs. the flush manure systems. These differences reflect the nature of the different manure handling systems.

Bulk tank milk yield (32.2 vs. 32.5 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 (Table 5). Concentration of milk urea nitrogen tended to be lower during the low-protein periods (13.3 vs. 14.5 mg/dL, respectively) and income-over-feed-costs increased by $0.62/cow/d 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 2011 Midwestern section meeting of the American Society of Animal Science (Des Moines, IA), the 2012 national meeting of the American Dairy Science Association (New Orleans, LA; see attached abstract), 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).

Participation Summary

Education

Educational approach:

As indicated earlier, 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 2011 Midwestern section meeting of the American Society of Animal Science (Des Moines, IA), the 2012 national meeting of the American Dairy Science Association (New Orleans, LA; see attached abstract), 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). Finally, a full-length manuscript is being currently prepared for publication in the Our Industry Today section of the Journal Dairy Science.

No milestones

Additional Project Outcomes

Project outcomes:

Impacts of Results/Outcomes

The project demonstrated that a reduction of dietary 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/cow/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. The impact of the project on feeding practices in the Northeast is difficult to assess, but the feedback we are getting from producers and consulting nutritionists is that low-protein feeding of dairy cows is being adopted by farms across the region. As an example of this, in a recent project funded by the National Fish and Wildlife Foundation, we had difficulties identifying dairies in two Pennsylvania watersheds (Mifflin and Lancaster Counties) that feed diet with crude protein above 17%. This is a clear indication that dairy producers realize the benefits of low-protein diets, such as significantly lower feed cost and more environmentally-friendly dairy industry.

Economic Analysis

Feed cost is the largest expense on any dairy farm. As discussed above, the dietary intervention that resulted in a 23% reduction in manure ammonia emissions also decreased feed costs and increased income-over-feed-costs by $0.62/cow/d. Expressed on an annual basis for a 100-cow dairy, these savings amount to over $22,500.

Farmer Adoption

All participating farms continued to feed reduced-protein diets after completion of the project. Although forage composition continuously changes, the feedback we received from the cooperator dairies was that they strive to feed dietary protein levels close to the animal requirements, which is significantly lower that the usual dietary protein levels in the Northeast (close to or above 17%).

The impact of the project on feeding practices in the Northeast is difficult to assess, but the feedback we are getting from producers and consulting nutritionists is that low-protein feeding of dairy cows is being adopted by dairies across the region. As an example of this, in a recent project funded by the National Fish and Wildlife Foundation, we had difficulties identifying dairies in two Pennsylvania watersheds (Mifflin and Lancaster Counties) that feed diet with crude protein above 17%. This is a clear indication that dairy producers realize the benefits of low-protein diets, such as significantly lower feed cost and more environmentally-friendly dairy industry.

Assessment of Project Approach and Areas of Further Study:

Areas needing additional study

We conducted a survey of 59 dairy nutritionists from the Northeast to determine the roadblocks for adoption of low-protein diets (survey questions are attached). Of the returned surveys, the most probable cause for not implementing low-protein feeding strategies was concern for reduced production. This outcome clearly demonstrates the need to further propagate the benefits of low-protein diets and lack of negative effects on productivity when the diet is properly formulated. Another very important issue, specifically in Pennsylvania, is the lack of participation and knowledge among Plain community farmers. This project was unfortunately not able to address this community. We are slowly trying to make progress in this area but a lot more is needed.

Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the view of the U.S. Department of Agriculture or SARE.