China is a great agricultural nation and has abundant straw resource. The production of annual crop by-products, such as, wheat and rice straw and maize stover, is about 7.0 billion tons which is more than 50 times of grass production in north campo of China. If the maize stover of whole country might be processed or treated with zymolytic method or other methods as the ruminant’s feed, the fermented fodder which amount to 40 million tons could save 50 percent fodder grain annually. It will not only administer to resolve the problem of short-commons in China, but also ameliorate structure of meat supply for consumers. Here we conducted three experiments to investigate the species of additive and their mode of action on promoting the degradation of crop residuals. 

In the first experiment, cellulose and lactic acid bacteria (LAB) were added to ensiling maize stover. Their effects on silage and in vitro fermentation characteristics were assessed. Before ensiling there were substantial variations in chemical composition between the fractions of maize stover (P < 0.001). Leaf blade had the highest content of crude protein (CP), but the lowest contents of neutral detergent fiber (aNDF) and water soluble carbohydrates (WSC). Leaf sheath had the highest aNDF content but the lowest contents of CP and neutral detergent soluble, and the whole stem fraction had the highest WSC content. Lactic acid concentrations in untreated silage were in the order: whole stem> whole maize stover > leaf sheath > leaf blade. Losses of dry matter (DM) and aNDF were in the order: leaf blade > leaf sheath > whole maize stover > whole stem. Addition of either cellulase or LAB accelerated (P < 0.05) degradation of WSC, increased lactic acid concentrations of the silage, reduced losses of DM, aNDF and CP during ensiling and enhanced the metabolizable energy level as estimated from 26 h gas production. Effects depended on the level of additives. To improve silage quality, a cellulase preparation was more effective on maize stover fractions that contain high aNDF and acid detergent fiber than LAB, while LAB was better than cellulase for the fraction with highWSC content than cellulase. (Sun et al. Anim. Feed Sci. Technol. 2009)

In the second study, yeast culture and fibrolytic enzyme (containing cellulase and xylanase) were directly added to crop straw (i.e. rice straw, wheat straw, maize stover, and maize stover silage). Their effects on in vitro fermentation characteristics of crop straw were examined using an in vitro gas production technique. Results showed that supplementation of yeast culture increased the cumulative gas production, theoretical maximum of gas production, rate of gas production, IVDMD, and in vitro OM disappearance (IVOMD), and decreased the lag time for each type of straw. Fibrolytic enzyme supplementation tended to increase cumulative gas production, theoretical maximum of gas production, and rate of gas production; prolonged lag time of gas production; and enhanced IVDMD and IVOMD for 4 types of cereal straws, with the significance of this effect being dependent on the level of supplemented enzymes. There were significant interactions between fibrolytic enzymes and yeast on all in vitro gas production parameters, IVDMD, and IVOMD of each type of straw. The outcome of this research indicated that the application of fibrolytic enzyme preparation and yeast culture could improve in vitro gas production fermentation of cereal straws. (Tang et al. J. Anim. Sci. 2008)

In the third study, the effects of 3 nonionic surfactants (NIS), including alkyl polyglucoside (APG), sorbitan trioleate (Span85), and polyoxyethylene sorbitan monostearate (Tween80), on in vitro fermentation characteristics of maize stover, rice straw, and wheat straw were examined using an in vitro gas production technique. Results showed that the NIS generally increased the in vitro maximal gas production (A), but decreased the lag time of cereal straws. The effects of NIS on the rate of gas production (B) were related to the surfactant type and fermented substrate. The NIS generally increased IVDMD and in vitro OM disappearance (IVOMD) of cereal straws, but responses were dose dependent. The NIS increased total VFA maize stover and wheat straw, but decreased total VFA concentration for rice straw. The effects of NIS on the molar proportions of acetate, propionate, and butyrate were dependent on the dose and type of NIS and on fermented substrate. Several interactive effects were noted between or among 3 surfactants (APG, Span85, and Tween80) on in vitro gas production variables, IVDMD, IVOMD, and VFA for each straw; the optimal combinations of 2 or 3 types of NIS were determined according to the responses of IVDMD and IVOMD to NIS addition. The results of this study suggest that NIS may improve in vitro fermentation of low quality roughages and have potential application as feed additives in ruminant production. (Cong et al. J. Anim. Sci. 2009)

Therefore, large-scale utilization of additive will hold promise for enhancing the degradation of high fiber content forage in ruminants.