BONUS MAGAZINE AUTUMN 2025

Milk Urea Nitrogen (MUN) What they are and do they matter? Elzanne Fourie - Technical Advisor: Dairy Milk Urea Nitrogen (MUN) is an important source of information that can be gathered from a milk sample. Many factors influence MUN levels, and these levels can indicate if there are issues present in the diet, or a lack thereof. What is MUN? MUN stands for Milk Urea Nitrogen, and it is a value that indicates the quantity of urea excreted in the milk of a dairy cow. Urea can also be released from the cow via urine and saliva. The standard unit for MUN is mg/dl. Regarding MUN levels, 10-14 mg/dl is a good benchmark for a milk sample, though acceptable levels may vary between breeds. How is MUN produced MUN is produced when rumen microbes are unable to convert rumen-degradable protein into microbial protein. Instead of becoming microbial protein, excess nitrogen found in protein sources is converted into ammonia. This ammonia is absorbed into the bloodstream, where it is redeposited in the liver and converted to urea. From there, the urea is passed on via the bloodstream to the urine and milk. Low MUN levels Low MUN levels, less than 10 mg/dl, are common when feed sources lack protein or when protein in the total diet is improperly Average MUN levels Average MUN levels, in the ideal range of 10-14 mg/dl, are what one should aim for in a milk sample analysis. This indicates that the diet is well-balanced, and that no energy is wasted or underutilised in the process of milk production. At these levels, a dairy cow is performing efficiently. balanced. Below-average MUN levels typically indicate that rumen microbes do not have sufficient levels of rumen-degradable protein to function optimally. This often results in reduced production and potentially decreased milk protein in the sample. Low MUN levels can be corrected by adding a good quality source of rumen-degradable protein in the correct quantity to balance the total dietary protein. Adding urea to the diet, as recommended by a nutritionist or technical advisor, can also help elevate MUN levels. High MUN levels High MUN levels, typically starting at 16 mg/dl and above, indicate an excess of protein in the www.agribonus.co.za Autumn 2025 BONUS 33