Abstract
To clarify in vitro digestibility of wheat straw and Japanese redwood sawdust substrate, the edible mushroom (Pleurotus ostreatus) was cultivated under conditions conductive to fruitbody production. After adjusting the moisture content to between 65-70%, either chopped straw or sawdust was packed tightly into bottles. The bottles were then sterilized and subsequently inoculated with P. ostreatus. Straw substrate, straw substrate mixed with an eutrophic (wheat bran) at 20%, sawdust substrate and sawdust substrate mixed with eutrophics (wheat bran, rice bran and bean curd refuse) at 45% were compared. The incubation period lasted 8 weekd with fruitbody formation being induced after 4 weeks, sampling was performed throughout the incubation period. In the sawdust only substrate the spread of the mycelium was arrested at about 4 weeks and fruitbody yield was higher when substrates were mixed with eutrophics. Dry matter content of the substrates decreased by between 4.3-22.1% during incubation and was particularly reduced in fruitbody harvested substrates. In the sawdust substrates the content of both hemicellulose and cellulose remained stable. In the straw substrates the hemicellulose content decreased by more than 40% during the 8 weeks while the cellulose content remained relatively stable, though cellulose content of straw substrates decreased at fruitbody formation. The rate of decrease of ADL was higher in straw than in sawdust and was reduced in substrates mixed with eutrophics. The Ce-DMD of both straw substrates decreased early in the incubation period and then increased by between 12-26% after 4 weeks of incubation while the Ce-DMD of sawdust mixed with eutrophics decreased from 38.5% to 21.6% during the 8 weeks of incubation. The digestible dry matter (DDM) of straw substrate increased by 11% but the DDM content of straw substrate containing wheat bran in which fruitbody formation had occurred was less than the DDM content prior to incubation.
