Milk urea is an approximate indicator of the amount of crude protein in a cow’s diet. It is formed from the metabolism of absorbed amino acids and body protein.
Interpreting MU Values
Recommended dietary crude protein (CP) requirements and the approximate MU levels at different stages of lactation are shown in the table below.
|Early lactation||Mid lactation||Late lactation|
|Minimum CP% in diet||18||16||14|
|Approximate MU (mg/dl)||25-40||25-30||20-25|
In Kenya pasture-based systems, MU levels are higher than in systems where cows are fed a total mixed ration (i.e. USA, Western Europe). This is due to the high amount of crude protein (about 20%) in good quality pasture.When pasture makes up more than 60% of the diet (low-input systems) MU levels can often be greater than 30 mg/dl. Research suggests that these high MU values are not detrimental to the health or reproductive performance of the cow.When pasture is less than 60% of the diet (higher-input systems) MU may be used as a tool to help guide ration changes (e.g. help to decide when to put in or to pull out expensive protein supplements).
Factors affecting milk urea
The main factor affecting MU in pasture-based systems is the amount of protein in the diet. Other factors include water intake, cow condition, stage of lactation, season, genetics, milking frequency, rumen health, and liver function among others.
- Milk urea info sheet
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