Effect of methanol on methanogenesis and fermentation in the rumen simulation technique (RUSITEC)

The semicontinuous rumen simulation technique (RUSITEC) was used co investi gate the effect of methanol on methane production and ruminal fermentation. Ten fermentation vessels were fed daily, on a dry matter basis, 8.3 g hay, 3.5 g concentrate and 3.7 g pectin. Five of these vessels were given a dai ly dose of 24.7 mmol methanol, raising methanol concentrations in the rumen fluid about eight to ten times above the level in the control vessel (3.5 mmol/l at 1 h) from 1 to 7 h after feeding. Methanol disappeared from the c ontrol and methanol-treated fermenters with closely comparable half lives o f 3.7 and 3.6 h, respectively. After 24 h only trace amounts of methanol re mained in the rumen fluid. The methanol supply increased methane production from 16.0 to 23.6 mmol/day, reflecting an enhanced activity of methylotrop hic methanogenic archaebacteria. Other fermentation characteristics, pH, re dox potential, degradation of feed constituents, ammonia and volatile fatty acid production did not respond co methanol, except for a significantly re duced iso-valerate production. In conclusion, RUSITEC proved to be a respon sive fermentation system to investigate the methanogenic potential of metha nol as a constituent in feedstuffs for ruminants.