Improving air quality and dairy profitability through reduced protein feeding

2008 Annual Report for ONE07-075

Project Type: Partnership
Funds awarded in 2007: $9,997.00
Projected End Date: 12/31/2009
Region: Northeast
State: Pennsylvania
Project Leader:
Eugene Schurman
Penn State Cooperative Extension

Improving air quality and dairy profitability through reduced protein feeding


Research on the amount of ammonia produced daily by dairy cattle has been very limited, however, numerous studies are now being conducted to help answer this question. We do know that the level of protein (crude and soluble) can have an effect on potential ammonia production. It is highly likely that many dairy producers are feeding excess protein in the diet of their lactating cows. In the past, this was a common recommendation by many dairy nutritionists as an insurance measure. However, excessive protein feeding is expensive in addition to the potential for causing ammonia production and air quality issues. Dairy producers along with their dairy nutritionists need to look closer at protein quality and solubility and formulate rations that are more nitrogen efficient. Adding energy sources that capture excess nitrogen produced in the rumen may help. Rations need to be formulated using metabolizable protein (MP) instead of crude protein (CP). Using ration balancing programs such as the Cornell Net Carbohydrate and Protein System model (CNCPS) or the Cornell University, University of Pennsylvania, and Minor Agricultural Research Institute (CPM-Dairy) dairy ration formulation software program by a dairy nutritionist may help to improve nitrogen utilization. This could improve economic returns to the dairy producer to make their operations more sustainable and reduce potential ammonia production in the urine and limit what can volatize into the atmosphere.

Twelve dairy producers from Southwest Pennsylvania have agreed to participate in this two year study to demonstrate that by reducing the feeding of excess protein to lactating dairy cows, farm profitability and ultimately sustainability can be improved. Some of this overfed protein is being linked to reduced reproductive performance and increased risk of nitrogen loss into the environment. With the recent emphasis by the U.S. Environmental Protection Agency to improve air quality, dairy and livestock farms are being scrutinized because of their potential as large contributors of atmospheric ammonia. Although more research is needed to quantify these emissions, the dairy and livestock industry expects that some reductions will be required of them. This project seeks to work with dairy producers to take a proactive approach to lowering ammonia production and emissions.

This study will involve the following:

Monitoring dairy ration crude and soluble protein, starch and non-fiber carbohydrates levels.

Monitoring milk urea nitrogen levels.

Monitoring milk yield and reproductive performance.

Conduct workshop(s) for dairy producers and dairy nutritional consultants to emphasize the economic and environmental importance of reducing excess protein feeding to lactating dairy cattle.

Objectives/Performance Targets

The purpose of the study is to demonstrate to dairy producers that by following NRC 2001 recommended dietary guidelines for CP, the subsequent milk yield, milk components, and reproductive performance will not be negatively affected. Based on current research, all these parameters should improve. This will improve farm profitability and sustainability. Also, even though ammonia emissions will not be monitored on these farms, the current best management practices available to dairy producers consist of feeding cows rations balanced for protein and carbohydrate fractions so animals can utilize protein more efficiently. Previous and current research indicates that this strategy should lead to reduced ammonia production in the animal and subsequent loss into the atmosphere.


As a result of participating in the SARE Air Quality Project, 100% (N=12) of the participants have either maintained or lowered the crude protein content of their lactating cow rations to 17% or less. NRC recommends 17% or less. The average actual crude protein for the 12 participants was 16.5.

As a result of participating in the SARE Air Quality Project, 67% (N=12) of the participants have lowered their milk urea nitrogen which serves as an indicator of excess protein feeding. The average for the 12 participants at the start of the project was 12.3 and currently it is at 12.1.

As a result of participating in the SARE Air Quality Project 100% (N=12) of the participants had no significant decrease in milk yield or milk components as a result of lower ration crude protein levels. The average for the 12 participants at the start of the project was 69.9 lbs. and currently it is at 71.7 lbs.

As a result of participating in the SARE Air Quality Project 100% (N=12) of the participants had no significant increase in calving interval. The average for the 12 participants at the start of the project was 13.8 and currently it is at 14.0.

To put things in perspective, prior to precision feeding taking off, rations were being routinely formulated for crude protein at 17.5 to 18.5% on a dry matter basis, which exceeds the cow’s requirement for that nutrient most of the time. For MUNs, there is some disagreement over the ideal range. Some researchers recommend 10 to 14 milligrams per deciliter (mg/dl) while others recommend 8 to 12 mg/dl. The later range reflects rations that are formulated to the cow’s requirement for protein and excel in the balance of protein, protein fractions, and carbohydrates to capture excess ruminal ammonia.

Question 1. On average, nutritionists are formulating rations with lower protein values, table 1. However, the protein level on some farms is still too high for the current level of milk production. There is opportunity to formulate the protein level closer to requirements.

Question 2. On this project, many of the farms consistently have very good agreement on the protein level in the TMR analysis compared to the formulated ration. Other farms have more variability, however, on average they come very close to the formulated diet.

Question 3. For this project, the MUNs have been matching very closely to the actual protein values. The largest discrepancy in actual and formulated crude protein values are the herds maintaining MUNs between 10-12 mg/dl. These herds have consistently tested lower in their protein value compared to the formulated diets. The herds with average MUNs ranging from 12.1 to 16 mg/dl have had very good agreement in protein levels and as expected, the herds with the highest MUNs have had the highest average protein values.

Nutritionists have really come to the plate to change the way in which they formulate diets for protein. This has been extremely challenging since protein level can have a tremendous impact on milk production if not properly implemented on farm. We are definitely seeing ration formulation moving in a positive direction. There are still opportunities for improvements, related to feeding management practices and moving the protein levels down even further to more closely match production.

Two popular press articles were submitted and published in “Lancaster Farming” and “Farmshine” magazines. Titles of the articles were “Precision Feeding for Protein and the Effects on MUNs” and “How Far has Pennsylvania Come in Precision Feeding – Phosphorus?”


Kevin George

Brent Lowmaster

Leroy Bergbigler

George Hartzell

Robert Graham

Mark Gardner

Ralph Lieb

Jan Itle

Tom McNutt

Rodney Bloom

Ronald Learn

Tom Wallace