Abstract
Blood and milk samples were taken simultaneously from 17 dairy cows to determine concentration of urea nitrogen. Dry chemical autoanalyzer (DRICHEM) was used to determine blood urea nitorogen (BUN) and milk urea nitrogen (MUN). Significant correlation (r=0.982, P<0.01) was observed between concentrations of BUN and MUN. Although significant correlations were observed between DRICHEM and 3 other methods (r=0.891-0.941, P<0.01)(Absorbance, Differential pH, and Infrared spectroscopy), nosignificant correlation was observed with the quick dipstick method. In samples stored at room temperature, MUN concentrations decreased significantly at 24 h after sampling. In the right front quarter of the udder, significant difference was observed in MUN concentration between pre-milking and post-milking. MUN concentrations increased after feed intake and reached a peak from about 3 to 5 h after feeding.
