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United States Department of Agriculture

Agricultural Research Service

Title: Effect of Animal and Nutritional Factors on the Relationship Between Milk Urea N and Blood Urea N in Lactating Cows

Authors
item Broderick, Glen
item Clayton, M - UNIV OF WISCONSIN-MADISON

Submitted to: Journal Dairy Science Supplement
Publication Type: Abstract Only
Publication Acceptance Date: July 17, 1996
Publication Date: N/A

Technical Abstract: Milk urea N (MUN) will serve as a valuable index of protein utilization in the lactating cow if it accurately reflects the concentration of blood urea N (BUN). Increasingly, MUN is being used in practice to identify diets with inadequate or excess amounts of CP. Published and unpublished data collected in 11 trials with lactating cows fed 31 different diets were used dto begin a statistical evaluation of animal and nutritional factors that may influence MUN concentrations. Linear regression of MUN on BUN from 797 observations yielded the equation: MUN (mg N/dL) = .508 x BUN (mg N/dL) + 5.86 (P < .001; r2 = .381). However, modifying the relationship between MUN and BUN to take into account additional diet and cow information can result in a model with an r2 in excess of .90. Most of this additional variation that was accounted for was associated with the cow. We are adding data from 12 more trials with 43 more diets to continue to explore the nature of the relationship between MUN concentration and animal and nutritional factors.

Last Modified: 9/10/2014
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