Dr. Chris Dutton, VMD

Since rolling out our new MUN report earlier this summer, we’ve had some questions on how the information provided can be applied to pasture based or grazing herds. Dr. Chris Dutton, a member of Agricultural Management Resource Support Team, was one of the team members involved with the development of the new MUN report. He addresses the opportunities for grazing herds receiving the MUN report below.

I’m a grazer. I just got the new MUN report and my MUNs are way high.  What are my opportunities?

High quality pasture has more nitrogen than a cow needs.  When a cow gets excess nitrogen in her diet, she exports nitrogen as urea. The cow expends energy to make this urea, which leaves the body via milk and urine.  When milk urea nitrogen (MUN) is high, the cow is using energy to discard urea that it could be using for milk production.  So, if you have high MUNs, you can save money by removing protein, a source of nitrogen for the cow, from your grain mix.  Many grazers quite successfully reduce costs and increase production by decreasing the protein in their grain during peak grazing.

If you already are feeding very small amounts of grain, you may still have an opportunity.  To a reasonable degree, nitrogen from pasture can be “captured” and used by the cow to make milk if it is fed in concert with an energy source.  If they are together in the rumen at the same time, free nitrogen and energy can combine to make useful protein for the cow to absorb.  We know that grass in the evening has more energy in it than grass in the morning, so grazing in the evening can decrease MUN and increase milk production.  Feeding energy sources that release their energy later, while cows are on pasture can decrease MUN and increase milk.  Many farmers commonly use beet pulp for this.  If you have a feeder for pasture supplementation, feeding energy grains to cows on pasture helps.   Finally, we can force nitrogen to stay in the rumen for a long enough time for our energy sources to combine with it and make protein by feeding long stem hay immediately before cows go to pasture.

Now that you have these tricks to decrease your MUN and make more milk it is time to experiment with the help of your nutritionist.  You have the data to fine tune your operation.

My MUNs are low.  What are my opportunities?
Urea is made in a cow’s liver as it normally processes protein.  As a result, some milk urea nitrogen (MUN) in your milk is normal.  If MUN levels are low in a cow, she would efficiently use more protein if you gave it to her.  The value of milk protein is far outweighs the cost of protein in the feed, so this is an easy way for you to make more money.  Feed more protein.  Measure MUN to fine tune your feeding.

We often see low MUN levels when forage levels of protein are not what we think they are.  Your forage and pasture contribute a significant amount of protein for your cows.  If we do not  check the levels of protein often enough we can short change our cows and loose milk.  Milk MUN levels will let you know how your forage or pasture is contributing to a steady cow diet.