Abstract
A protease present in an enzyme preparation may digest other enzymes and thus reduces the effectiveness of an enzyme preparation to improve digestibility of animal feeds. Thus the effects of enzyme mixtures with or without proteases were tested on the digestibilities of crude protein (CP) and dry matter (DM) in corn soybean mixture (CSBM) in vitro. The effects of cellulase, xylanase, pectinase, hemicellulase, glucanase, phytase, commercial enzyme (Energex) or protease inhibitor on digestibilities were also examined. The cellulase significantly improved CP digestibility measured by the pepsin-pancreatin method. However, protease, phytase, pectinase, xylanase, glucanase, and hemicellulase had no effect on the CP digestibility. On the other hand, CP digestibility was significantly increased by the mixture of all the enzymes used, and its effect was further improved when protease was excluded from the enzyme mixture. When protease inhibitor, leupeptin, was added in the combination of all enzymes, digestibility was further improved. Although Energex had no effect on CP digestibility of CSBM, CP digestibility tended to be improved when protease inhibitor was added. Any of single enzyme and their combination did not have significant effects on DM digestibility of CSBM. In conclusion, the present results strongly suggest that cellulase improves CP digestibility of CSBM whereas protease inhibits the actions of these enzymes. Omitting proteases from commercial enzyme preparations may improve their actions on digestibility.
