Effectiveness of selected fibrolytic enzymes on in vitro digestibility of maize (Zea mays) stover
An in vitro experiment was conducted to determine the effectiveness of three exogenous fibrolytic enzymes namely cellulase, xylanase and pectinase on dry matter (DM), organic matter (OM) and neutral detergent fibre (NDF) digestibility of maize stover. Cellulase, xylanase and pectinase were added on ground stover individually at a rate of 3g/kg DM maize stover and in combination at a ratio of 50:50. The in vitro dry matter digestibility (IVDMD) of maize stover ranged from 41.6% (control) to 54.8% (cellulase-pectinase combined), a significant increase of up to 24.2%. Combining pectinase with cellulase or xylanase significantly (p<0.05) improved the IVDMD by 24.2% and 20.5%, respectively, compared to when pectinase was applied alone (16.3%). The range for in vitro organic matter digestibility (IVOMD)of maize stover was 31.7% (control) to 45.9% (cellulase, xylanase and pectinase combined). Amongst the enzyme treatments, pectinase had a significantly (p<0.05) lower IVOM digestibility of 41.5% compared to cellulase-xylanase (45.4%), cellulase-pectinase (45.7%) and cellulase-xylanase-pectinase (45.9%), but it was comparable (p>0.05) to xylanase, cellulase and xylanase-pectinase. It was observed that not all the enzymes and enzyme combinations influenced in vitro neutral detergent fibre digestibility (IVNDFD). Improvement (p<0.05) in IVNDFD was observed when maize stover was supplemented with cellulase-xylanase and cellulase-pectinase only. Enzymes applied singly did not (p>0.05) improve IVNDFD. Compared to the control (26.3%), cellulase-pectinase (31.4%) and cellulase-xylanase (33.2%) had significantly higher IVNDF digestibility (p<0.05), resulting in improvements of 16.3% and 20.9%, respectively. The selected exogenous fibrolytic enzymes were effective in degrading maize stover, whether singly applied or in combination, compared to maize stover without enzyme supplementation. Cellulase-pectinase and cellulase-xylanase combinations were highly effective in degrading maize stover.
Keywords: Exogenous fibrolytic enzymes, in vitro dry matter, in vitro neutral detergent fibre, maize stover
