Title: Correlations of Milk Urea Nitrogen Levels with Casein, Whey and Non-Protein-Nitrogen Levels in Cows Milk
Abstract: Milk total protein (crude protein; CP), casein, whey, nonprotein nitrogen (NPN), urea-N (MUN) and plasma glucose, acetate and 3-hydroxybutyrate (3-HB) of 134 pair milk and blood plasma samples from 45 dairy cows were measured. Negative correlations were observed between casein and whey as well as between whey and NPN, and there was no correlation between casein and NPN. Whey proportions in CP were higher in the samples with lower MUN levels. The MUN/NPN ratios were higher with increasing MUN levels. Higher MUN levels were observed in many samples with lower plasma acetate or 3-HB levels. Plasma glucose, acetate or 3-HB levels were not correlated with the other milk protein fractions.