This fact sheet has been developed to support the implementation of the Natural Resources Conservation Service Feed Management 592 Practice Standard. The Feed Management 592 Practice Standard was adopted by NRCS in 2003 as another tool to assist with addressing resource concerns on livestock and poultry operations. Feed management can assist with reducing the import of nutrients to the farm and reduce the excretion of nutrients in manure.
The Natural Resources Conservation Service has adopted a practice standard called Feed Management (592) and is defined as “managing the quantity of available nutrients fed to livestock and poultry for their intended purpose”. The national version of the practice standard can be found in a companion fact sheet entitled “An Introduction to Natural Resources Feed Management Practice Standard 592”. Please check in your own state for a state-specific version of the standard.
Protein is typically the most expensive purchased component in dairy rations. Protein is composed of a number of nitrogen (N) sources. The goal in feeding dairy cattle is to develop feeding programs and management systems that maximize the efficiency of N use and decrease N excretion to the environment. This provides an opportunity to increase both profitability and environmental stewardship.
How can you determine the efficiency of N use in your herd? There are a couple of methods that can be used to do this on your farm. One is to monitor the milk urea nitrogen (MUN) levels. High MUN levels indicate a lower efficiency of N use in the animal. A separate fact sheet contains more information and guidelines for using MUN as part of your feeding management system.
A second way is to calculate the quantity of the feed N consumed that ends up in milk. Milk nitrogen efficiency (MNE) is a term that can be used to quantify this relationship. A higher MNE value indicates that more of the feed N consumed was captured in the milk. This also indicates that N excretion to the environment was reduced.
What are the ranges observed for MNE? This question was examined using two sets of data. One was from published research trials and consisted of 334 rations from 62 different research trials (Chase, 2003). The rations fed in these studies ranged from10.2 to 24.6% CP. A second set was 83 rations from 49 commercial dairy herds. Results from this evaluation were:
What can you do to improve your herd’s MNE value? The following items should help with this:
Milk nitrogen efficiency provides a method to assess the efficiency of feed N use in your herd. Higher MNE values indicate better efficiency in convert feed N into milk N. These higher MNE values also indicate that less of the feed N is being excreted into the environment in the manure. Profitability, measured as income over feed cost, should also be improved since you are getting better use of your feed dollar.
Chase, L.E. 2003. Nitrogen utilization in dairy cows – what are the limits of efficiency? Proc. Cornell Nutr. Conf., Syracuse, NY. pp: 233-244.
How can I calculate the MNE value for my herd? Table 1 provides a worksheet that can be used to do this. The following guidelines can be used to interpret the results of this calculation:
|<20%||This indicated a very low efficiency of N use and a high level of N excretion to the environment.|
|20-25%||Better. There are opportunities to improve the efficiency of N use.|
|25-30%||Similar to the averages observed in both the research and commercial herd data. You should evaluate ration adjustments to increase MNE.|
|30-35%||Great! There may still be some opportunities for improvement.|
|>35%||Super! Make sure that this is not the result of low CP rations that may be slightly deficient or have lowered milk production.|
|MNE Calculation||Your Herd||Example|
|a. Ration dry matter intake, lbs/day||____||55|
|b. Ration crude protein, % of total of dry matter||____||17|
|c. Milk production, lbs/cow/day||____||85|
|d. Milk total protein, % (If milk true protein data is available, multiply by 1.08 to get total protein)||____||3.2|
|e. Crude protein fed/cow/day, lbs (a*b/100)||____||9.35|
|f. Crude protein in milk, lbs (c*d/100)||____||2.72|
|g. Daily feed N intake, lbs (e/6.25)||____||1.5|
|h. Daily milk N output, lbs (f/6.38)||____||0.43|
|MNE,% = (h/g)*100||____||28.7|
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This fact sheet reflects the best available information on the topic as of the publication date. Date 4-12-2007
This Feed Management Education Project was funded by the USDA NRCS CIG program. Additional information can be found at Feed Management Publications.
This project is affiliated with the LPELC.
Larry E. Chase
Extension Dairy Nutritionist
Cornell University, Ithaca, NY
Mike Hutjens – University of Illinois
Floyd Hoisington – Consulting Nutritionist