Effect of urea form and method of feeding on rumen ammonia concentration.

Rumen ammonia was compared in six rumen fistulated, lactating Holstein cows fed urea twice daily in a concentrate mixture, urea fed once per day in a complete ration, and a gelatinized starch-urea product fed twice daily in the concentrate mixture. Samples were taken during 24-h intervals at the end of each 3 wk. Sharp and similar peaks in rumen ammonia followed feeding of urea and gelatinized urea-starch product twice daily in the concentrate mixture. A much lower ammonia peak followed the once daily feeding of the complete ration. Use of complete rations offered ad libitum eliminates the need for products with sustained ammonia release.