In vitro Fermentation, Microbial Profile and Methanogenesis of Two Fibrous Feeds as Influenced by Exogenous Fibrolytic Enzyme Cellulase

Abstract

Batch cultures of buffered rumen fluid were used to evaluate the use of exogenous fibrolytic enzyme, cellulase (CE) as a potential means of improving ruman fermentation and reducing methanogenesis of two fibrous feeds, Guinea grass (Panicum mximum) and rice straw (Oryza sativa). The enzyme CE was applied at 50 (T l), 100 (T2), 150 (T3) and 200 (T4) pi for 0.5 g ground (1mm) substrates including a control (without CE). Triplicates were incubated in vitro in a completely randomized design (CRD) followed by further incubation with the enzyme. Gas production at different time intervals during the in vitro incubation of 24 hours, methane (CHJ %, in-vitro dry m atter digestibility (IVDMD), Ammonia nitrogen (NH3-N) and protozoa populations in fermented liquid were estimated. Supplementation of the CE significantly enhanced (P < 0.05) in-vitro gas production (IVGP) and IVDMD (For Guinea grass T l, 51.2% ; T 2 ,50.3% ; T3, 50.8% ; T 4 ,50.3% and Control, 43.5% : For rice straw T l, 3 6 .2 % ; T2, 36.3% ; T3, 36.7% ; T4, 37.2% and Control, 32.0% ) irrespective of substrate. The ruminal NH3-N production in Guinea grass was significantly increased (P < 0.05) whereas no significant improvement was observed for NH3-N production in rice straw. The ruminal protozoa population was significantly reduced compared to the control in both substrates. Supplementation of CE significantly (P< 0.05) suppressed the percentage CH4 production for Guinea grass (Control, 0.0 2 5; T 4 ,0.014) where no significant difference was observed for rice straw (Control, 5.01; T4, 5.27). It is concluded that supplementing CE has the potential to improve IVDMD, ruminal NH3-N production while suppressing protozoa population and CH4 production.