Effects of treating high forage and high concentrate diets with exogenous fibrolytic enzymes on their in vitro ruminal fermentation

摘要

Batch cultures of mixed rumen microorganisms were used to study the effects of a 24 h pre-treatment with a xylanase from Trichoderma viride (XYL) and a cellulase from Trichoderma longibrachiatum (CEL) on the in vitro fermentation of two diets composed by grass hay and concentrate in the proportions of 70:30 (HF) and 30:70 (HC). In 8 h incubations with HF, CEL increased (P＜0.05) the production of acetate, propionate and total volatile fatty acids (VFA) and gas, but no effects (P＞0.05) were observed for XYL. In contrast, with HC both enzymes increased (P＜0.05) the production of propionate and total VFA and the true DM degradability of substrate, and decreased the CH4/VFA ratio (P＜0.05). After 24 h incubation, some of the observed effects disappeared, but CEL still increased (P＜0.05) the production of acetate, propionate and total VFA for HF. For HC, both enzymes increased (PO.05) the production of total VFA and XYL also increased (P＜0.05) acetate production. The results indicate that effects of enzymes on in vitro fermentation were influenced by the nature of the diet, and that this influence varied with the incubation time, being more pronounced at short incubation times.