Effect of Steam Explosion on In Vitro Gas Production Kinetics and Rumen Fermentation Profiles of Three Common Straws

Abstract

To investigate the effect of steam explosion on in vitro gas production (GP) and rumen fermentation profiles of common straws, in vitro cultivation was conducted for 96 h with the rumen fluid collected from steers. Different types of straw had various chemical compositions, which were affected by steam explosion (P<0.01). Steam explosion increased (P<0.01) the rate and volume of GP, lag time disappeared and asymptotic GP decreased, which were also affected (P<0.01) by the type of straw. The type of straw influenced (P<0.05) the final pH, while steam explosion exerted an effect (P<0.01) on the ammonia-nitrogen concentration. The proportions of individual volatile fatty acid (VFA), except acetate (A), differed (P<0.05) among the feeds. Steam explosion increased total VFA production and the proportion of propionate (P), while decreased the proportions of A, isobutyrate and valerate as well as the ratio A/P (P<0.01). The type of straw had an effect (P<0.05) on the activities of avicelase and carboxymethyl cellulase (CMCase), while steam explosion increased (P<0.01) the activities of avicelase, CMCase, β-glucanase and xylanase. The available energy concentrations and digestibilities differed (P<0.01) in the feeds and were increased (P<0.05) with steam explosion processing. The interaction straw type×treatments was significant (P<0.05) for most monitored parameters. These results suggest that steam explosion could improve rumen fermentability and energy utilisation of straw, being an effective pre-treatment method in feed industry.