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.
The purpose of the study is to demonstrate to dairy producers that by following the 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.
- Twelve dairy producers were originally asked to participate in the study and all 12 completed the study.
An informational meeting was held with the nutritionist for each of the herds to explain the objectives of the study and their role in the study.
TMR (total mixed ration) samples were taken and analyzed at the start of the study to determine the crude protein baseline level for each herd.
TMR (total mixed ration) samples were taken and analyzed every two months to monitor the crude protein in the diet. In addition, as a follow-up to a previous NESARE Partnership Grant on dairy ration phosphorus levels, TMR phosphorus levels were monitored.
TMR nutrient specification sheets were submitted every two months by the nutritionist to correspond with the TMR sampling. They were used to determine how close the crude protein in the TMR fed matched what was being formulated.
Milk (bulk tank) samples were taken and analyzed at the start of the study to determine the MUN (milk urea nitrogen) baseline level for each herd. Milk urea nitrogen provides an accurate measure of how much nitrogen is absorbed by the cow but not used for growth or milk protein synthesis.
Milk (bulk tank) samples were taken and analyzed every two months to monitor MUN (milk urea nitrogen).
The Penn State Precision Feeding Tool was used with all 12 herds to evaluate the nutrition, feeding management, and forage quality on each of the farms.
Milk yield and milk components were monitored monthly using both Dairy Herd Improvement (DHI) and producer bulk tank milk weights.
Reproductive performance was monitored monthly using Dairy Herd Improvement (DHI). Previous research has shown excessive feeding of protein can have a negative effect on reproductive performance.
The Penn State Dairy Profit Tool was used with all 12 herds to determine profitability/sustainability at the start of the study.
- As a result of participating in the SARE Air Quality Project, 75% (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 16.3%.
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 14.7 and currently it is at 12.0. For the duration of the project, eight farms maintained MUNs between 10-12 mg/dl. These levels are reflective of the TMR protein levels holding at 16%. The other four herds consistently maintained MUNs between 13-15 mg/dl and their average TMR protein level was 17.2%. There was a tendency for higher protein to result in higher MUNs, however, examining the sampling periods, this trend did not always show up, especially during different times of the year (i.e. temperature affect).
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 69.6 lbs. and currently it is at 69.7 lbs. There were discrepancies in the actual milk produced on farm compared to what the nutritionist formulated. Three herds averaged 11-15 pounds higher in milk compared to the formulated, three herds averaged 9-12 pounds lower than formulated, five herds were very close and one herd never had milk production listed on the paper ration.
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.
Using the 2001 NRC model to compare dry matter intake with respective milk production, 64% (N=12) of the herd’s actual dry matter intake matched with what the cows averaged in milk production. One herd was very inefficient with intakes too high for the actual production. Two herds consistently had lower intakes for the level of milk produced and they happened to be the highest producing herds of the group, averaging 78 pounds. When comparing actual intakes to the formulated, actual intakes were consistently lower, approximately 2.5 pounds on average over the course of the project. The difference ranged from 1.0 to 5.0 pounds lower than formulated. Another observation was the formulated rations rarely deviated in dry matter intake or the milk production formulated during the course of the project. There was a lot of variation in actual dry matter intake over the course of the project on each farm, regardless of herd size.
There were some interesting observations comparing the TMR analysis with the formulated diet. The dry matter percent of the TMR was significantly lower compared to the formulated diet by 3.5% (46.84% vs. 50.41%). The crude protein percent was significantly lower by 0.85% for the actual versus the formulated (16.43% vs. 17.38%). These discrepancies may not appear to be extreme, but they could become an issue as nutritionists balance protein closer to the cow’s requirement. Rations that are not implemented properly could result in diet protein levels that could be too low and result in less than optimum performance.
The phosphorus levels in these herds were very encouraging. There was extremely good agreement between what the nutritionist formulated and what came back in the TMR analysis. Using actual intakes and milk production, phosphorus as a percent of requirement was good with 10 herds maintaining between 100-110% of requirement. Two of the herds were at 114% and 119% of requirement. The average phosphorus percent for the two high herds was 0.34% and 0.42% respectively. The herd with the average phosphorus of 0.34% was the herd with very poor dry matter intake efficiency. Also, for the 10 herds doing extremely well, the phosphorus percent ranged from 0.35 to 0.42%. This is a perfect example why “balancing” for a certain phosphorus percent is not ideal. It is going to depend on what the cow is eating and how much she is producing.
- At the completion of the study, a survey was sent to the 12 producers to assess if any management changes would occur because of the project results. Of the 9 producers who responded:
100% would now monitor MUNs routinely as an indicator of under or over feeding protein.
89% would now monitor dry matter intakes to compare to the formulated diet.
78% would now monitor crude protein levels in the TMR to compare against the formulated diet.
All nine producers said they would spend more time discussing ration changes with their nutritionist and 78% would implement feed strategies if there is the potential to minimize nitrogen excretion.
Eight producers said they were somewhat to moderately likely to start monitoring income over feed costs as a tool to manage monthly cash flow and improve profitability.
Education & Outreach Activities and Participation Summary
Outreach efforts have included the publication of two popular press articles in “Lancaster Farming” and “Farmshine” magazines. Titles of the articles were “Precision Feeding Crucial for Protein and the Effects on MUNs” and “How Far has Pennsylvania Come in Precision Feeding – Phosphorus?” A third article titled “How Well is Dairy Embracing Precision Feeding?” has been submitted for publication in the “Hoard’s Dairyman” magazine. Two workshops have been conducted for nutritionists to make them aware of the precision feeding concept to reduce both excessive feeding of protein and phosphorus. A workshop is planned for the SW Regional Dairy Day which will utilize both producer participants and their nutritionists in a panel discussion of how they are implementing precision feeding concepts.
The Penn State Dairy Profit Tool was used with all 12 herds to determine profitability/sustainability at the start of the study. Because of the down turn of the dairy economy (low milk prices) and the volatile input prices in the past year, a final analysis was not conducted as most farms will show negative profits for 2009.
- In the survey, when asked why is it more dairy producers don’t implement feeding strategies which help minimize nitrogen excretion and the potential of ammonia emissions, the responses were:
Many dairy producers don’t understand the cost associated with feeding excess protein and are unaware of the potential environmental impact.
Fear of change and possible potential loss of milk production.
Many nutritionists are more focused on high milk production without concern of cost or environmental impact.
Also, in the survey, when asked why is it that more dairy producers don’t monitor their Income Over Feed Costs as a tool to manage ration costs and monthly cash flow, especially now with lower milk prices, the responses were:
Time and ability to track all income and expenses.
Very difficult to monitor all inputs.
Many dairy producers rely solely on their dairy nutritionist to formulate least cost rations without questioning ingredient selection and costs.
Many dairy producers don’t understand dairy nutrition and the many options available and are fearful of making any changes. Thus, they rely on their nutritionist to make many of their economic decisions.
Areas needing additional study
In summary, based on the 12 herds evaluated, dairy nutrition is moving in the right direction regarding the levels (percents) of both protein and phosphorus being formulated and what is observed in the TMR analysis. There are still discrepancies between the formulated and actual diets, which is a big component of precision feeding. Getting a better handle on actual dry matter intake is still a challenge. There are opportunities for the nutritionist and the producer to make improvements on the side of ration development and implementation and perhaps even improve the income over feed costs. 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 latter 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.
There is still a need to educate dairy nutritionists as well as dairy producers about the concept of precision feeding. 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.
Further study is needed and will be continuing with a NESARE Research Grant Project titled “Improving the Efficiency of Nitrogen Use and Reducing Ammonia Emissions from Pennsylvania Dairies.” This study will look not only at crude protein levels in the TMR, but at actual ammonia emissions at the cow level.