The Effects of Altering the Protein Efficiency of Lactating Dairy Cows on the Whole-Farm Nitrogen Efficiency of Dairy Farms

1999 Annual Report for SW99-024B

Project Type: Research and Education
Funds awarded in 1999: $19,184.00
Projected End Date: 12/31/1999
Region: Western
State: Utah
Principal Investigator:

The Effects of Altering the Protein Efficiency of Lactating Dairy Cows on the Whole-Farm Nitrogen Efficiency of Dairy Farms


Software to quantify nitrogen and phosphorus balances on livestock farms was beta tested
in the western ree-ion., and distributed via the internet to users in 35 states and 38
countries. Our lab assisted with development of two papers on use of the software to
characterize nutrient balances in the western region of the US. We also tested the use of
milk urea nitrogen to estimate diet crude protein, and we compared 14 different DHIA
laboratories across the country for milk urea analysis. We updated comprehensive web
pages that disseminate information on reducing nutrient losses from agriculture.

Objectives/Performance Targets

The objectives of the overall project are as follows:
1) to verify the usellness of milk urea nitrogen (MUN) analysis for accurately
predicting aspects of N metabolism,
2) to determine the potential use of herd MTJN averages and recently developed
computer worksheets for predicting N losses and whole-farm efficiencies on
commercial dairies in UT and ID, and
3) to disseminate all results to dairy producers, extension personnel and scientists via
extension publications, the World Wide Web, and peer-reviewed journal articles.
Our contribution to the overall project is based on the following specific objectives:
1) to improve computer worksheets for calculating whole farm balances by adapting
them to the western region and by implementing changes identified by using the
worksheets in this region,
2) to assist with evaluation and improvement in MTJN analysis based on research
conducted at Utah State University, and
3) to disseminate information from this project to farmers via extension publications and
the World Wide Web.


We made numerous changes to the software as a result of difficulties found in adapting it
to the region. For example, we needed the capability to enter more feeds per farm. In
addition, the practice of applying manure to legumes was added. The software refined by
the project is available for download from our web site and it has been downloaded by
more than 141 sites in 27 countries and 25 states.
The model we developed was evaluated under western US conditions by the investigators
in Utah. While most of the equations were shown to be accurate under different
conditions, the prediction of urinary nitrogen excretion as a function of MUN differed
hmth e original model We showed that DHIA laboratories began to report MUN that
was about 4 mdd lower starting in Sep. 1998. Thus, the model was modified to reflect
current measurement practices. A refereed journal article on these differences was
accepted by the Joumal of Dairy Science. In addition, DHIA laboratories around the US
were compared for the way the same milk samples were analyzed for MUN. The
laboratories that use various wet chemistry methodologies yielded similar results, but
laboratories using NIRS for MUN analysis resulted in different results depending on the
laboratory. Predicting urinary nitrogen excretion from milk urea nitrogen requires use of
a wet chemistry procedure for MUN analysis. An article in the Joumal of Dairy Sciences
is under review.
Several extension publications were developed to disseminate this information to dairy
farmers. Our World Wide Web site ( ives
2000 to 5000 visits per month. Extensive information on using MUN and improving herd
N utilization efficiency is available on the site. This information was updated this year to
reflect changes in measurements made by DHIA laboratories.

Impacts and Contributions/Outcomes

Dairy farmers can use MUN to fine tune diets and prevent overfeeding or underfeeding of
protein to their cows. The work we conducted will make it possible for farmers to use
this technology more effectively. If they reduce overfeeding of cows, it will reduce their
cost of feed because protein is an expensive ingredient. In addition, cows use energy to
excrete the excess nitrogen. Thus, by not overfeeding, energy costs or lost production
can be reduced. In addition, with less protein being fed, less N will be excreted in
manure. This effect will make it easier to comply with field-by-field nutrient
management plans. Many farmers in the west export their manure to the nearest
available land. By reducing- N in manure, the distance the manure must be shi-p -p ed is
reduced. Finally, reducing N excreted to manure will reduce ammonia-N volatilization,
N runoff, and N leaching proportionally. The software for calculating nutrient balances
can be used to help farmers and consultants understand the balance of nutrients on their
farm and to quantify the unaccounted for N and P. These unaccounted for nutrients may
accumulate in soils or be lost to the environment.