Animal Science, Department of


Date of this Version

January 2008


Published in 2008 Nebraska Beef Cattle Report. Copyright © 2007 The Board of Regents of the University of Nebraska.


Ruminally and duodenally fistulated Holstein steers were fed at 40% and 85% of ad-libitum intake. Microbial purine:N ratio did not differ between intake levels, which makes estimating microbial protein easier in production or experimental settings. Urinary purine derivatives (PD):creatinine (PD:C) ratio and microbial CP flow estimated from the duodenum increased with the higher feeding level. Urinary PD:C and duodenal purine flow were related, suggesting that urinary PD:C ratio can be used to estimate relative differences in microbial CP flow.