Abstract:

This research investigated the effects of cellulase， xylanase and their combination on the structural and water-soluble carbohydrate components， in vitro digestion characteristics and fermentation quality of rice straw silage. Four treatments were set up as follows： 1） 0.3% distilled water， control （CO）； 2） 0.3% cellulase （CE）； 3） 0.3% xylanase （XE）； 4） a mixture of 0.15% cellulase and 0.15% xylanase， combined enzyme group （CX）. Samples were taken and analyzed after 3， 7， 14 and 30 days of ensiling. Compared to the CO treatment， CE， XE and CX treatments had significantly （P<0.05） higher lactic acid， glucose， fructose and sucrose contents， but significantly （P<0.05） lower pH values， ammonia nitrogen， total volatile fatty acid， acid detergent fiber， neutral detergent fiber， cellulose and hemicellulose contents and dry matter loss. The enzyme additives significantly （P<0.05） increased the cumulative gas production at 24， 48 and 72 hours and in vitro dry matter digestibility of rice straw silage. The CX treatment had the highest （P<0.05） lactic acid content （34.13 g·kg^-1 DM）， in vitro gas production （68.27 mL）， in vitro dry matter digestibility （61.31%） and the lowest pH value （4.36） at the end of ensiling. In addition， the CX group had numerically （P>0.05） or significantly （P<0.05） higher glucose， fructose and sucrose contents than CE and XE groups during ensiling. In summary， the addition of enzymes promoted the degradation of structural carbohydrates， increased the water-soluble carbohydrate content， and improved the fermentation quality and in vitro digestibility of rice straw silage. The CX treatment performed better than the CE and XE treatments， as indicated by superior fermentation quality， higher carbohydrate degradation and conversion， and better in vitro digestion characteristics.

Key words: cellulase, xylanase, rice straw, fermentation quality, in vitro digestion characteristics