Experiment 1. Rumen fluid was obtained from a rumen-fistulated steer about 12 hr post-
prandial. The steer had been fed ad libitum a ration containing 66.6% alfalfa hay (IRN 1-00-063) and 33.4% sorghum grain (IRN 4-04-378). A mineral supplement containing salt and dicalcium phosphate was offered freechoice. The tureen fluid was incubated with substrates conraining coffee grounds to determine their effect
on microbial activity.