ARS | Publication request: APPLICATION OF MILK UREA NITROGEN VALUES

Submitted to: Symposium Proceedings
Publication Type: Proceedings
Publication Acceptance Date: August 15, 2007
Publication Date: N/A

Technical Abstract: Statistical analyses using both linear and multi-component regression and mixed effects models have been applied to a number of databases relating milk urea nitrogen (MUN) to factors important for N utilization in lactating dairy cows. Concentrations of MUN are highly correlated to BUN, which is a strong indicator of N-inefficiency. Concentrations of MUN were most closely related to dietary crude protein (CP) content, but were less strongly influenced by dietary energy content and estimated ruminal protein degradability. MUN was also highly correlated with milk protein yield as well as ruminal ammonia concentration and rumen N-balance. Equations predicting urinary-N excretion from MUN are very precise, particularly one estimating urinary-N excretion using MUN output in milk and CP content of the diet. In practice, MUN must be analyzed under standard conditions and several cows fed a specific diet (a minimum of 4, but preferably as many as 16) should be sampled to have sufficient confidence that the MUN value is reliable. Overall, proper application of MUN data has the potential to optimize production and greatly improve N-efficiency and reduce N emissions from dairy production.