The effect of phosphoric phenyl ester diamide as inhibitor of the rumen urease of dairy cows 2. metabolism of nitrogen 15 labeled urea
Voigt, J.; Krawielitzki, K.; Piatkowski, B.
Archiv fuer Tierernaehrung 30(10-12): 825-834
Two lactating dairy cows supplied with rumen and duodenal re-entrance cannulae were fed 8.2% vegetable crude protein 180 g urea/day (I) or urea treated with the urease inhibitor phosphore phenylester diamide (PPD, 1% of the N-quota). The cows, accustomed to urea, received the PPD-urea without (II) and with a 30-day adaptation (III) to PPD. On the 1st day of the experiment 1/2 of the urea was given ruminally in its 15N-labeled form. Two hours after the isotope supplementation, 62.5 and 24 mg NH3 and 6.58 and 21 mg urea/100 ml could be detected in the rumen juice of I to III. Within 72 h, 16.6, 26.1 and 25.2% of the 15N-excess given (15N') passed the duodenum in TCA [tricarboxylate] soluble form and 31.2, 28.4 and 41.7% in TCA precipitate form. Of the total amount of 15N, 15.6, 24.4 and 21.5% were excreted in urine and 4.5, 4.6 and 6.0% in the milk protein. The values for feces were 14.4, 14.4 and 15.4%. With a limited inhibition of rumen urease by PPD as it develops after the adaptation, the utilization of urea-N can be improved.