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

Authors: Varel, Vincent; KREIKEMEIER KELL - 5438-01-07; JUNG HANS-JOACHI - 3640-10-00

Submitted to: Applied and Environmental Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/19/1993
Publication Date: N/A
Citation: N/A

Interpretive Summary: Various research studies have indicated that yeast and fungi cultures, when added to animal diets, have the ability to stimulate animal production by either increased weight gain, milk production or total tract digestibility of feed components. Little is known about how this production efficiency many occur. The objectives of our studies were to evaluate a fermentation extract from a fungal microorganism for its ability to enhance the degradation of grass forages when added to ruminal microorganisms in a test tube. The fungal extract increased the degradation of the fiber components of bromegrass 28% over control samples after 12 hours; however, no difference was seen after 24 hours. Depending upon the concentration of fungal extract added to fermentation tubes containing switchgrass, an increase from 12 to 24% in the degradation of switchgrass was seen. The number of microorganisms in the fermentation tubes which contained fungal extract were three-times greater than control tubes. These studies indicate that the fungal extract helps the rate of breakdown of fiber components in grasses, but does not affect the total extent of grass degradation. Thus, animals fed fungal extract should have increased feed intakes, because their initial rate of fermentation is predicted to be greater. Animal studies are in progress to determine this.

Technical Abstract: Aspergillus oryzae fermentation extract (Amaferm) was evaluated for its ability to influence degradation of bromegrass and switchgrass fiber fractions by mixed ruminal microorganisms in vitro. Concentrations of Amaferm approximating those that may be found in the rumen ecosystem, 0.06 mg/ml, increased the degradation of bromegrass neutral detergent fiber (NDF) by 28% after 12 h fermentations, but had no effect at 24 or 48 h. Degradation of both the cellulose and hemicellulose fractions at 12 h were increased. Additions of 0.08 and 8% (vol/vol) Amaferm filtrate stimulated degradation of switchgrass NDF 12 and 24%, respectively, at 12 h; while 80% filtrate decreased degradation 38%. Total anaerobes in culture tubes containing 80% filtrate were 5 times greater than controls, however, cellulolytic organisms were 3.5 times less than controls. This suggested that the filtrate contained high concentrations of soluble substrate which did not allow the cellulolytic organisms to compete well with other populations. Remaining concentrations of esterified p-coumaric and ferulic acids were lower at 12 h in NDF residues from fermentations supplemented with Amaferm. Because total anaerobes were not inhibited in fermentations containing Amaferm, antibiotics are unlikely to be involved as a mode of action for increasing NDF degradation. The 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 esters is discussed.