An in vitro technique (Theodorou, 1993) to determine the Dry Matter degradation by measuring the amount of gas produced may reduce the need for in situ degradability studies. A strong relationship has been shown for cereal straws (Blummel and Orskov 1993) but little work has used concentrate feeds. Washing a feed contained in a dacron bag will remove a fraction containing soluble material and fine particles. The relative contributions of these components to the gas production in vitro is unknown. This work investigated if removal of this ‘a’ fraction from concentrate feeds used in vitro would improve the relationship with the in situ degradablility.

Samples of four feeds, winter beans (WB), soyabean meal (SBM), rapeseed meal (RSM) and spring barley (SPB) were ground through a 1mm screen. Half was machine washed in a dacron bag of pore size 43 um using a cold water cycle to provide the Washed feed (W) and the remainder left Unwashed (UW).