Effects of micronised wood powder irradiated with ultraviolet light and exposed to ozone gas on in vitro ruminal fermentation in beef cattle

In in vitro ruminal fermentation, micronised wood powder is digested to produce volatile fatty acids, but its fermentability is weak. The aim of the present study was to ascertain a suitable pretreatment of micronised wood powder to enhance volatile fatty acid production in vitro. Rumen fluid taken from beef cattle was anaerobically incubated with micronised wood powder. Initially, effects of particle size of micronised wood powder on ruminal fermentation were examined. Volatile fatty acid production was then evaluated by slightly reducing methanol-soluble substances such as lignin in micronised wood powder. Further, micronised wood powder that had been irradiated by an ozone lamp (185 and 254 nm) or sterilisation lamp (254 nm) was fermented in rumen fluid. The lack of volatile fatty acid production by rumen fermentation of untreated micronised wood powder was not associated with its particle size. In the methanol-treated micronised wood powder, volatile fatty acid production was increased, and this response was sensitively dose-dependent. Moreover, pretreatment by ozone lamp irradiation stimulated micronised wood powder fermentation and resulted in increased volatile fatty acid concentrations, especially of acetate and propionate. The response to ozone-treatment of micronised wood powder increased propionate more than acetate. In addition, this pretreatment of micronised wood powder to improve rumen fermentation was superior to that with a sterilisation lamp (254 nm). Therefore, the ruminal fermentability of micronised wood powder was not dependent on its particle size. The present study suggested that irradiation by ozone lamp is useful to enhance micronised wood powder digestibility and that this treated powder may become a lignified biomass feedstuff capable of volatile fatty acid production in ruminants. *Correspondence to: Dr. Yoshio Hamano, Field Education and Research Center, Faculty of Bioresource Sciences, Akita Prefectural University, Ohgata, Akita 010045, Japan; E-mail: [email protected]