Effects of different nonionic surfactants on in vitro fermentation characteristics of cereal straws1

The effects of 3 nonionic surfactants (NIS), including alkyl polyglucoside (APG), sorbitan trioleate (Span85), and polyoxyethylene sorbitan monostearate (Tween8O), on in vitro fermentation characteristics of maize stover, rice straw, and wheat straw were examined using an in vitro gas production technique. Four levels each of APG, Span85, and TweenSO [0, 0.02, 0.05, and 0.1% (vol/vol) of incubation solution] were tested in a 4 x 4 x 4 factorial arrangement. 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 concentration of in vitro fermentation supernatant for maize stover and wheat straw, but decreased total VFA concentration for rice straw. The effects of MS 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 Tween8O) on in vitro gas production variables, IVD-MD, 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. [PUBLICATION ABSTRACT]