This is just a reflection of the amount of crude protein in the diet. Diets high in crude protein will have a high MUN content in the milk. The optimum range for MUN is between 20 and 35mg/100ml.

Lush grass at this time of year is high in crude protein and can cause MUN levels to rise above 40. While it does take energy for the cow to process this, there is no economic cost to this as excess dietary protein is just a byproduct of the cheapest feed available – grass.

Furthermore, there is no correlation between MUN levels and herd fertility performance in grazing animals so it’s really a non-issue. The only thing is that where MUN is on target or high, there is no need to feed a high protein meal as it is just adding to the excess crude protein in the diet.

Look for a nut or buy a straight with low crude protein at 12 to 14%.

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