In vitro and in vivo ruminal fermentation of micronised wood powder for volatile fatty acid production in beef cattle

The aim of the present study was to evaluate in vitro and in vivo ruminal fermentation of micronised wood powder in beef cattle. Micronised wood powder was prepared by pulverizing sapwood of Japanese cedar to a mean particle size of 52 μm. Ruminal fluid from four beef cows was anaerobically incubated with different amounts of micronised wood powder (50, 100, 200, or 400 mg per 30 ml rumen fluid) for 24 hours at 39°C. In the in vivo experiment, four cows were fed micronised wood powder for four weeks in a crossover design. During the initial feeding period of seven days, micronised wood powder was gradually increased to the equivalent to 0.3% of body weight, and then animals were fed micronised wood powder for three weeks at this level. In batch fermentation, total concentrations of volatile fatty acid were increased by micronised wood powder supplementation except at 50 mg. This response was mainly attributable to increased concentrations of the major volatile fatty acids of acetate, propionate, and butyrate. However, volatile fatty acid production from micronised wood powder by in vitro ruminal fermentation was low and limited, even when the supplemented levels were increased to 400 mg. The ruminal fermentability of micronised wood powder was shown by the lack of change in the volatile fatty acid profile during in vivo ruminal fermentation. Therefore, the present study found that ruminal microorganisms enable fermentation and digestion of lignocelluloses in micronised wood powder directly for volatile fatty acid production. However, further consideration of micronised wood powder, such as improvement in particle size or lignin, is needed to accelerate the fermentation kinetics of micronised wood powder in the rumen. 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]