Changes over time in the bacterial communities associated with fluid and food particles and the ruminal parameters in the bovine rumen before and after a dietary change

This work aimed to study the changes over time in the bacterial communities associated with the fluid and food particle fractions of the cow rumen following a change in diet. Four cannulated cows were fed a hay-based diet for 21 days and were then switched to a corn-silage-based diet for 33 days. The bacterial communities were regularly characterized by capillary electrophoresis - single-strand conformation polymorphism (CE-SSCP) and qPCR, and the main ruminal parameters were determined. The dietary change led to slight reductions in the diversity index, bacterial concentration, pH, and NH3-N concentration, and to an increase in the redox potential and volatile fatty acid concentrations. CE-SSCP profiles were not significantly affected by the dietary change but did change over time, with frequent fluctuations in both fluid and food particle fractions before and after the dietary change. The food particle fraction had a higher diversity index of bacterial community (+1.2 points, P < 0.001) and slightly more total bacteria than the fluid fraction of the rumen.