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

At this stage of the project, the work with the 12 cooperator dairies was completed. A second sampling period was conducted in spring 2011. Similar to the fall’10 sampling event, the dairies fed low-protein diets. Diet composition was monitored for at least 2 wks before sampling and data collection. Average crude protein concentration of the diets was 15.3%, which was within our target of 1%-unit reduction (compared with the high-protein feeding period). Ammonia emissions were measured twice following the reduction in dietary protein. As before, milk production and income-over-feed costs were monitored before and after the reduction in dietary protein. Overall, the 1% reduction in dietary crude protein resulted in an average 36% reduction in ammonia emission from manure. Flush dairies emitted less ammonia from the barn floor than scrape or gravity-flow dairies. Average milk urea nitrogen concentration was also reduced (15.4 vs. 13.2 mg/dL, a 14% reduction) and income-over-feed-cost was increased by $0.90/cwt for the low-protein feeding periods. There was no difference in milk yield of the cows 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 held Nov 9-10th at the Holiday Inn, Grantville, PA.

In the coming months, results from the project will be presented and low-protein feeding practices discussed at various meetings with dairy producers and professionals. Some examples are: a dairy producers meeting in Mifflin County (Jan’12), the Southwest Pennsylvania Regional Dairy Day (March’12), the Farming for Success Field Day (June’12), and Penn State Ag Progress Days (Aug’12). We’ll be conducting a survey among Pennsylvania dairy nutritionists, including those who attended the project presentations at the Penn State Dairy Cattle Nutrition Workshop (Nov’11), probing their experience and willingness to promote low-protein feeding of lactating cows. Field days and popular articles (Farmshine, for example) are also being planned.

• PSU NE SARE project newsletter

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) or 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. Extensive forage and diet sampling was carried out throughout the project to verify dietary crude protein levels. Following consultations with the dairymen and their nutritionists, a 1%-unit drop in dietary protein was achieved in most dairies in the 2nd year of the project (Fall’10 & Spring’11). Barn floor and laboratory ammonia emissions were measured before and after the dietary protein reduction. So was milk yield per cow, milk composition (including milk urea nitrogen), and income-over-feed-cost. Following dietary protein reduction, barn floor ammonia emissions were reduced on average by about 65%, but the ambient temperature was 41°F during the low-protein feeding periods vs. 57°F for the high-protein periods. Our laboratory measurements, however, which truly represent the effect of feeding, also showed a dramatic, 36% reduction in ammonia emission due to the reduced dietary protein content. Overall, flush dairies emitted less ammonia from the barn floor than scrape or gravity-flow dairies. Average milk urea nitrogen concentrations were reduced (15.4 vs. 13.2 mg/dL, a 14% reduction) and income-over-feed-cost was increased by $0.90/cwt for the low-protein periods. There was no difference in milk yield of the cows (68.2 vs. 68.3 lbs/d, high- and low-protein periods, respectively). Data from 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 held Nov 9-10th at the Holiday Inn, Grantville, PA.

Impacts and Contributions/Outcomes

All project activities planned for 2011 have been completed. Farm samples and ammonia emissions were collected/measured in spring’11. Reduction of dietary crude protein by about 1%-unit resulted in at least 36% reduction in ammonia emissions from manure, did not affect milk yield, and increased income-over-feed cost by $0.90/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 held Nov 9-10th at the Holiday Inn, Grantville, PA.

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