IN-VITRO STIMULATION OF FORAGE FIBER DEGRADATION BY RUMINAL MICROORGANISMS WITH ASPERGILLUS-ORYZAE FERMENTATION EXTRACT

Aspergillus oryzae fermentation extract (Amaferm) was evaluated for it s ability to influence degradation of brome grass and switchgrass fibe r fractions by mixed ruminal microorganisms in vitro. Addition of Amaf erm at a concentration of 0.067 mg/ml, which is approximately the conc entration found in the rumen ecosystem (0.06 mg/ml), increased the deg radation of brome grass neutral detergent fiber (NDF) by 28% after fer mentation for 12 h (P < 0.01), but had no effect after fermentation fo r 24 or 48 h. The levels of degradation of both the cellulose and hemi cellulose fractions were increased after fermentation for 12 h (P < 0. 01). Additions of 0.08 and 8% (vol/vol) Amaferm filtrate (12.5 g/100 m l) stimulated degradation of switchgrass NDF by 12 and 24% (P < 0.01), respectively, after fermentation for 12 h; when 80% filtrate was adde d, degradation was decreased by 38%. The concentrations of total anaer obes in culture tubes containing 80% filtrate were 5 times greater tha n the concentrations in the controls; however, the concentrations of c ellulolytic organisms were 3.5 times lower than the concentrations in the controls (P < 0.05). These results suggested that the filtrate con tained high concentrations of soluble substrate which did not allow th e cellulolytic organisms to compete well with other populations. The r emaining concentrations of esterified p-coumaric and ferulic acids wer e lower at 12 h in NDF residues obtained from fermentation mixtures su pplemented with Amaferm. Because the total anaerobes were not inhibite d in fermentation mixtures containing Amaferm, antibiotics are unlikel y to be involved as a mode of action for increasing NDF degradation. T he possibility that Amaferm contains enzymes (possibly esterases) that may play a role in stimulating the rate of fiber degradation by mixed ruminal microorganisms by removal of plant cell wall phenolic acid es ters is discussed.