Why you should be looking at individual MUN

All herds on test with Dairy One are enrolled in our free MUN alert program. When more than 50% of a group, pen, or lactation stage is outside the desirable MUN range of 8-14, the farm will be directly emailed a Feed Management Diagnostic report.

Farms may also choose to enroll in the Feed Management Diagnostic program to receive individual cow MUN results (downloaded to DairyComp or PCDART) and the Feed Management Diagnostic report for each test day. Participation in this program is $0.08 per sample.

What is MUN?

Milk urea nitrogen is a key measure of how effectively the cow is using protein in her diet. MUN values that are higher than the recommended range generally indicate too much protein in the diet or that there is an imbalance between the protein and energy. This means the cows are not using their feed as effectively as possible. MUN values below the recommended range suggest the animals are not getting enough protein in the diet and could be sacrificing production.

What is missing if a farm strictly uses bulk tank MUN in evaluating their feeding management?

Cows with high milk production have a larger impact on the average MUN giving us a false sense of security by relying on a bulk MUN alone. Our goal is for every cow to have a correctly balanced diet as indicated by a MUN of 8-14 mg/dl.

When we test individual cows can we rely on average MUN to indicate proper feeding management?

Averages can be misleading and should be used with caution. If half of the cows in a herd have a MUN of 5 and half a MUN of 15, the average will be 10. This falls within the desired range, yet 100% of the cows in the herd had MUN of that range.

What should be the next step we look for in MUN results?

We can also look at the MUN by certain segments of the herd to identify opportunities within particular groups. This could be pens that are fed different rations or managed differently from others. It also could be the DIM designation called Phase of Lactation and even the Lactation Group, looking at age and size differences.

What are the expectations for different parts of the herd?
  • In general MUN increases as DIM increases (normal efficiency of utilizing diet components as DIM progresses).
  • MUN typically increases as parity increases, especially first lactation compared to others. (First lactation animals are likely still growing to mature size and protein utilization may be greater to allow for this growth).
  • The majority (50%+) of each pen should fall in the 8-14 MUN range. This shows consistency related to equal feed access, water, rest, and diet composition.
  • The less spread in the range below and above the average in each feeding management group the better. At a minimum the goal should be average +/- 6, if the average is 12 then the lowest cow should be 6 and the highest should be 18.

Here are some more examples of MUN reports.

Talk to your DHI technician about setting up an email for MUN alerts or enrolling in the Feed Management Diagnostic program. If you aren’t currently on test with Dairy One, email [email protected] to be connected with a DHI technician in your area.