Effects of addition of cell wall degrading enzymes on the chemical composition and the in sacco degradation of grass silage

Herbage (83% Lolium perenne and 17% Trifolium repens ) was harvested 15,28 and 42 d after second cut, and ensiled in 1.5 liter preserving jars either directly, at 20% dry matter (DM), or wilted (30 and 45% DM). Each variant was ensiled with and without a commercial preparation of cell wall degrading enzymes and stored for 90 d at 30°C. Samples were then incubated in nylon bags in the rumens of three cannulated cows for 3, 6, 12, 24, 48 and 288 h to study the in sacco degradation of organic matter (OM), crude protein (CP), and (hemi) cellulose.
Addition of cell wall degrading enzymes significantly decreased cell wall content. The magnitude Of the decrease was influenced by stage of maturity and DM percentage. Maturity increased the DM content as well as decreasing the effect of enzymes on cell wall components. Lactic acid content increased and the pH value and ammonia ( P < 0.05) decreased, indicating a greater extent of fermentation in the enzyme-treated silages. Enzyme treatment had no effect on the content of digestible OM estimated by in vitro incubations.
The undegradable fractions of OM, CP and cell wall components were not significantly changed by the addition of enzymes. The results suggest that the cell wall degrading enzymes affected the insoluble, rumen-degradable fractions, thereby increasing the instantly degradable fractions. Consequently, the calculated effective degradation of OM and CP in the enzyme-treated silages was significantly ( P < 0.05) higher than in the untreated silages.