Effect of Fibrolytic Enzymes and Regrowth Ages on Fermentation Profile and Nutrient Composition of Mombasa Grass and Elephant Grass Silages

Abstract

Two experiments were carried out to evaluate whether the addition of cellulase and/or xylanase enzymes interacts with regrowth age (RA) in mombasa grass (Megathyrsus maximus) and elephant grass cv. BRS Capiaçu (Cenchrus purpureus) to alter nutritive composition and fermentation profile. Mombasa and elephant grass plots were mowed and harvested at two different RAs (7- and 11-week for mombasa grass; 12- and 16-week for elephant grass). After forages were chopped, they received one of the following additive treatments: no additive (control), xylanase enzyme (300 mg/kg DM; XYL), cellulase enzyme (1 g/kg fresh matter; CEL) and cellulase + xylanase enzymes (same dosages as before; MIX), in a factorial arrangement of 4 (additives) × 2 (regrowth ages), with three replicates. Greater lactic acid and lower acetic acid, butyric acid and NNH₃ concentrations were observed for CEL in mombasa grass silage. Nevertheless, CEL decreased aerobic stability in elephant grass silages and increased effluent production in both species. For mombasa grass silages, lower fermentation loss and more extensive fermentation were observed for early harvest, while the opposite was observed for elephant grass silages. Cellulase improves the fermentation profile of Mombasa grass silage. The combined application of these enzymes does not appear to warrant recommendation. Further research is warranted to evaluate the synergetic effects of cellulase with chemical, absorbent and microbial additives.