The effect of enzyme and mild hydrothermal treatment on the nutritive value of barley grain and canola meal for dairy cattle

• Main Author: Gill, Catherine Suzanne
• Language: English
• Published: 2009
• Online Access: http://hdl.handle.net/2429/5805

High ingredient costs and a competitive market have promoted support for research by the feed industry to improve the utilization of protein and energy feedstuffs such as barley and canola meal. The objective of this research was to determine the feasibility of using enzyme and mild hydrothermal treatment to improve the nutritional value of barley grain and canola meal for use by dairy cattle. In experiment 1, barley which was subjected to p - glucanase , protease and xylanase enzymes and mild hydrothermal treatment, was evaluated using 48 h in vitro dry matter disappearance ( IVDMD ) , in vitro true digestibility (IVTD), acid detergent fiber (ADF) and neutral detergent fiber (NDF) analyses . A number of interactions (P < 0.05) were observed for the digestibility parameters. Results of fiber analyses were inconclusive . Overall , the addition of xylanase was found to be detrimental and the mild hydrothermal treatment did not have an effect on enzyme activity. The addition of protease and / or p - glucanase to barley suggest potential application that may be further investigated. In experiment 2, canola meal was subjected to protease, xylanase enzymes and mild hydrothermal treatment. Treatments were evaluated using IVDMD, IVTD, ADF and NDF . Significant interactions (P < 0.05) were observed for IVDMD , IVTD, ADF and NDF. The addition of moisture significantly increased (P < 0.05) IVDMD and IVTD. Protease also elicited an effect (P < 0.05) on the NDF content. From this experiment, similar conclusions to those in experiment 1 were drawn: neither xylanase nor mild heat treatment was effective in improving digestibility. However, the addition of protease to canola meal at an intermediate level of application improved it's digestibility significantly (P < 0.05). Fiber analyses resulted in a large number of interactions which produced variable responses . Experiment 3 evaluated the effects of the treatments on the fermentation characteristics of canola meal using the in vitro gas production technique. Rate of gas production was significantly (P < 0.05) affected by protease, wheras , the length of the lag phase was significantly affected by the interaction between protease and xylanase (P < 0.05). In general , the treatments increased rate and decreased lag time. Volatile fatty acid (VFA) analyses revealed a significant interaction (P < 0.05) between protease and xylanase . There was a positive linear/ relationship (P < 0.05) between the level of protease application and the ratio of acetate to propionate. Protease also had an effect (P < 0.05) on the ratio of butyrate to propionate. Xylanase also significantly (P < 0.05) both acetate and butyrate production relative to propionate. Results from experiment 3 indicated the application of protease at higher levels was beneficial in terms of improving the nutritional value of canola meal . From the work conducted in this thesis , it may be concluded , in the case of both barley and canola meal, that xylanase was detrimental to digestibility and that mild hydrothermal treatment did not improve enzyme activities. Many enzyme treatments increased the proportion of fiber, suggesting a shift in feed composition . The results of this study suggest potential applications of the treatment of barley with protease or a combination of protease and p - glucanase enzymes . Treatment of canola meal with protease between the levels of 0 . 0 1% and 0 . 0 5% (vol / wt) resulted in the greatest improvement in it's nutritive value for dairy cattle. The in vitro work presented in this thesis demonstrates the potential improvements with enzyme technology in the feeding quality of barley and canola meal fed to dairy cattle.