Effect of fibrolytic enzymes and an inoculant on in vitro degradability and gas production of low-dry matter alfalfa silage

BACKGROUND: The objective of this study was to investigate the effect of polysaccharide-degrading enzymes (a cellulase and a xylanase) alone or in a combination with a bacterial inoculant on fermentation parameters and in vitro degradability and gas production of low-dry matter (DM) alfalfa silage. First cut alfalfa (Medicago sativa L.), harvested at about 5% bloom stage [260 g kg^-1 dry matter (DM)] was ensiled in laboratory-scale silos without preservatives or preserved with formic acid, a cellulase (Cell), a xylanase, a cellulose/xylanase enzyme combination (Cell/Xyl), a lactic acid bacteria-based inoculant (Inoc), and a mix of Inoc and Cell (Inoc/Cell). Triplicate silos were opened on days 1, 3, 7, 15 and 60. RESULTS: Silage pH and ammonia N and total free amino acids concentrations were the lowest (P < 0.05) for the formic acid silage. Inoc and Inoc/Cell produced the highest (P < 0.05) lactate concentration in the 60-day silage. In vitro degradability of silage DM was not affected (P = 0.998) by treatment, but amylase-treated neutral detergent fiber degradability was increased (P < 0.05) by formic acid.Compared with the control (51.3 mL 100 mg^-1 silage DM), all treatments except Cell/Xyl increased (P < 0.001) the 24 h cumulative gas production. CONCLUSIONS: Overall, enzyme and lactic acid bacteria-based preparations had minor effects on silage fermentation in this experiment. The increased cumulative gas production indicates some preservation or liberation of fermentable organic matter with most treatments tested. It is not clear, however, to what extent this effect would impact silage ruminal degradability in vivo.