Fermentation tubes for in vitro digestion of forages

During in vitro digestion of forages by rumen microorganisms in polycarbonate centrifuge tubes, forage particles formed dense mats which were raised above the level of media by entrapped gas. This did not occur with polyethylene centrifuge tubes. In vitro organic matter digestion was higher in polyethylene than in poly-carbonate tubes. Vacuum infiltration of water into samples prior to inoculation increased in vitro digestion with both types of tubes but to a greater extent with samples of high than of low digestion. Regression analysis of in vivo digestibility on in vitro digestion showed that the lowest residual standard deviation was with polyethylene tubes and vacuum infiltration, but omission of vacuum infiltration gave satisfactory results.