Effects of 3 chemical treatments on in vitro fermentation of rice straw by mixed rumen microbes in the presence or absence of anaerobic rumen fungi.

Rice straw (Rs) was treated by a sodium chlorite/acetic acid mixture (Sct), ammoniation (At) and alkaline hydrogen peroxide (Athp) methods. The objective was to compare their degradation and fermentation products in the presence or suppression of anaerobic fungi. Significant differences (P < 0.01) in degradation of straws were observed during all periods of incubation with Sct having the highest digestibilities during the 48-h and 72-h incubations. The degradation of Sct straw was highest in both of the incubations with whole rumen fluid (WRF) and WRF plus cycloheximide. In sacco digestion followed the order of Sct > At > Rs > Athp. Suppressing fungal activity with cycloheximide resulted in a decrease in dry matter degradation, with concomitant decrease in total volatile fatty-acid concentration. While the suppression of fungal activity with cycloheximide depressed acetate and butyrate production, it favored an increase in propionate production.