Milk urea nitrogen (MUN) analyses can be
used to evaluate the nutritional status of dairy
herds and for fine tuning the feeding program.
MUN values >18 mg/100 ml indicate that
dietary protein is being wasted and feed costs
could be reduced with ration adjustments.
Higher than desired MUN values also indicate
the need for additional undegradable intake
protein (UIP; bypass protein) in the ration.
High MUN values can also indicate the need
for more nonstructural carbohydrates (NSC) in
the diet. MUN readings <14 mg/100 ml indicate
dietary crude protein deficiencies or too
much UIP in the ration. Reduced milk production
or low milk protein tests can occur
when feeding rations that produce low MUN
tests. Poor reproductive performance may be
the result of feeding rations that produce high
MUN measurements. Conception rates may be
reduced as much as 20 percentage points when
MUN is >18 mg/100 ml.
