Abstract
This investigation was conducted to evaluate nutritional condition in 32 dairy cows by using milk urea nitrogen (MUN) and milk protein concentrations as indicators. Relationships between MUN, milk protein concentrations and feeding condition were investigated at monthly intervals. MUN was positively associated with crude protein (CP)% and total digestible nutrients (TDN)% in dry matter and negatively associated with TDN sufficiency and the TDN/CP ratio. Milk protein concentration was inversely related to the same items. As MUN and milk protein concentrations are closely related to feeding condition, it is concluded that they are useful for evaluating nutritional condition. Ranges for normal MUN concentration in each lactation stage are as follows: early stage (1-100 days after parturition) 8.6-9.2 mg/dl, mid stage (101-200 days after parturition) 8.6-16.7 mg/dl, and late stage (over 201 days after parturition) 6.1-2.5 mg/dl. The corresponding ranges for milk protein concentration are as follows: early stage 2.80-3.31%, mid stage 3.09-3.53%, and late stage 3.35-3.91%.
