Evaluation of cellulolytic exogenous enzyme-containing microbial inoculants as feed additives for ruminant rations composed of low-quality roughage

摘要

The supplementation of ruminant diets with exogenous cellulolytic enzymes can improve their digestibility and feeding value. The objective of this study was to determine the effect of supplementing roughage (rice straw) and concentrate with inoculants containing four fungal strains (Pleurotus ostreatus,Phanerochaete chrysosporium,Trichoderma reeseiandTrichoderma viride) and four bacterial strains (Paenibacillus polymyxa,Bacillus megaterium,Bacillus circulansandBacillus subtilis), given separately or as a mixture, as a source of exogenous cellulolytic enzymes, on basic rumen parametersin vitro, including digestibility and methane production. A batch culture trial was used to select the best supplements, and a long-term rumen simulation technique (RUSITEC) was used to evaluate the effects ofP. chrysosporium,B. subtilis, and a 1 : 1 mixture of these two on dietary component digestibility and fermentation parameters. In the batch culture evaluation, there were significant increases in the organic matter (OM) digestibility, the total gas production expressed as ml/g of dry matter, the OM, the neutral detergent fibre (NDF) and the acid detergent fibre (ADF) of the supplemented rations, as compared to the control, excluding the rations supplemented withT. virideandB. circulans. In the RUSITEC, the ration supplemented with mixed inoculants showed significantly higher digestibility of crude protein, ether extract, NDF and ADF than did the ration supplemented with theP. chrysosporiumandB. subtilisinoculants. It can be concluded that the simultaneous use of fungal and bacterial exogenous cellulases on rice straw roughage improves its digestibility, without negative effects on other rumen parameters.