4/8/2024 0 Comments Bun normal range childHolsteins usually have a lower MUN value than other dairy breeds, e.g. When comparing MUN values in a herd between months, account for differences in sampling times.Īnother factor affecting MUN values is breed. The AM MUN value is usually lower than PM samples taken from the same herd. In addition, herds milked 3x tend to have higher MUN values than herds milked 2x. The time of feeding relative to milking time MUN values usually peak 3-5 hours after feeding. total mixed rations (TMR) versus component-fed herds, and cow eating patterns can affect MUNs. There are many factors affecting MUN values. Herds with an MUN above 12-14 mg/dl would have increased urinary N excretion and there would be opportunities for improvements. Researchers from the University of Wisconsin estimate that there is 2 mg/dl change for each one percentage unit change in protein when rations contain 15 to 18.5% protein. These values typically are associated with a ration protein level of approximately 16%. The later range reflects rations that are formulated to the cow's requirement for protein and excel in the balance of protein, protein fractions, and carbohydrates to capture excess ruminal ammonia. Some researchers recommend a range of 10 to 14 milligrams per deciliter (mg/dl) while others recommend at range of 8 to 12 mg/dl. There are various ranges reported for MUN, which can make interpretation challenging, Table 1. In addition, MUN values can be used to improve the efficiency of microbial protein synthesis, which may reduce N excretion into the environment. Because MUN is a breakdown product of protein, it can be used to monitor protein status of cows. Therefore, MUN values are representative of urea levels of blood and other body fluids. Urea nitrogen (N) levels in blood plasma, blood serum and milk of an individual cow are highly related. The body excretes blood urea in urine and milk. If bacteria in the rumen cannot capture the ammonia and convert it to microbial protein, the excess ammonia is absorbed across the rumen wall.Įxcess ammonia circulating in blood can be toxic and the conversion of blood ammonia to urea is the way to prevent this toxicity. Urea is produced in the liver from ammonia derived mainly from the breakdown of protein in the rumen and from normal daily metabolism of absorbed amino acids and body protein.
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