Effect of Diet Quality on Adenosine-5′-triphosphate Concentration and Adenylate Energy Charge of Rumen Microbes from Fistulated Cows

Abstract

Two fistulated, nonlactating Holstein cows were fed a high quality diet of dairy concentrate mixed with corn silage or a low quality diet of weathered hay. Both animals were adapted in turn for 6 wk to the high quality and then to the low quality diet prior to sampling of rumen contents. The high quality diet was fed daily as a single meal; the low quality diet was fed ad libitum. Rumen fluid from cows fed the high quality diet had higher concentrations of adenosine-5′-triphosphate (42.98 versus 17.28 nmoles/ml), total volatile fatty acid concentrations (except acetic acid), total cell numbers (1.48 versus 1.12×1010/ml), and inorganic phosphorus (155.4 versus 91.8mM) and lower concentrations of adenosine-5′-diphosphate (6.80 versus 10.62 nmoles/ml) and adenosine-5′-monophosphate (3.41 versus 4.99 nmoles/ml) than when the low quality diet was fed. Adenylate energy charge, the ratio of adenosine-5′-tri- and .5 diphosphate to the sum of adenosine-5′-tri-, di-, and monophosphates was higher in the rumen contents of cows when the high quality diet was fed (i.e. .871 versus .685). Energy charge may be a useful tool to determine the energy adequacy of a diet to provide optimum growth conditions for the rumen ecosystem.