Effects of combined treatments of lactic acid bacteria and cell wall degrading enzymes on fermentation and composition of Italian ryegrass (Lolium multiflorum Lam.) silage

This experiment was carried out to study the effects of lactic acid bacteria (LAB) inoculation and addition of cell wall degrading enzymes on the fermentation characteristics and chemical compositions of Italian ryegrass silage. An inoculant LAB with or without a cell wall degrading enzyme of Acremoniumcellulase (A), or Meicellulase (M) or a mixture of both (AM), was applied to 1 kg of fresh Italian ryegrass sample. The treatments were control untreated, LAB-treated (application rate 10(5) cfu/g fresh sample), LAB + A 0.005%, LAB + A 0.01%, LAB + A 0.02%, LAB + M 0.005%, LAB + M 0.01%, LAB+M 0.02%, LAB+AM 0.005%, LAB+ AM 0.01% and LAB + AM 0.02%. The sample was ensiled into 2-L vinyl bottle silo, with 9 silages of each treatment were made (a total of 99 silages). Three silages of each treatment were incubated at 20, 30 and 40 degrees C for an approximately 2-months storage period. All silages were well preserved as evidenced by their low pH values (3.79-4.20) and high lactic acid concentrations (7.71-11.34 % DM). The fermentation quality and chemical composition of the control untreated and the LAB-treated silages were similar, except that for volatile basic nitrogen (VBN) content was lower (p < 0.05) in the LAB-treated silages. LAB + cellulase treatments improved the fermentation quality of silages by decreasing (p < 0.01) pH values and increasing (p < 0.01) lactic acid concentrations, in all of cellulase types and incubation temperatures. Increasing amount of cellulase addition resulted in further decrease (p < 0.01) of pH value and increases (p < 0.01) of lactic acid and residual water soluble carbohydrate (WSC) concentrations. LAB + cellulase treatments reduced (p<0.01) NDF, ADF, hemicellulose and cellulose contents of silages compared with both the control untreated and LAB:treated silages. LAB+cellulase treatments did not affect the silage digestibility due to fact of in vitro dry matter digestibility (IVDMD) was similar in all silages. The silages treated with cellulase A resulted in a better fermentation quality and a higher rate of cell wall reduction losses than those of the silages treated with cellulases M and AM. Incubation temperature of 30 degrees C seemed to be more suitable for the fermentation of Italian ryegrass silages than those of 20 and 40 degrees C.