Alkali treatment increases the digestibility of straw but processing methods and the effectiveness differ widely. The aim of this study was to compare an on-farm method producing chopped straw (C) with an industrial process producing coarsely ground straw (Viton) (G) (Wilson and Brigstocke, 1967).

Four dry Friesian cows, each with a large rumen cannula and a simple cannula in the proximal duodenum, were given (kg dry matter (DM)/day): 3.4 concentrate (180 g crude protein/kg DM) and 3.1 C or G alkali-treated straws in one meal daily in a simple change-over design. A single batch of spring barley straw was used and was treated with about 40 g NaOH/kg either by an on-farm process giving particles about 10 cm long (C) or by an industrial process giving coarsely-ground straw in a pellet (Viton) (G). Spot samples of digesta were taken from the duodenum for measurement of digestion in the stomach, using chromic oxide paper, and for measurement of the rate of passage of indigestible residues using magenta-stained straw. Eating behaviour and reticular movements were measured by use of balloons (Balch, 1971). Straw DM digestibility was measured over 48 h in vitro and by dacron bags (in situ) (Ørskov and McDonald, 1979).