Microscopic studies of structure and ruminal fungal colonization in sheep of wheat straw treated with different alkalis

The effect of chemically treating wheat straw (straw) with calcium oxide (C aO), Sodium hydroxide (NaOH) and alkaline hydrogen peroxide (AHP) on its su bsequent colonization and degradation by rumen fungi was followed in sacco in the rumen of sheep. The colonization of treated straws was compared with untreated counterparts microscopically using a trypan blue lactophenol sta ining technique to reveal the fungal thalli and rhizoids. Structural disint egration of straw particles caused by chemical treatments was also observed . AHP caused the greatest fragility to straw particles followed respectivel y by NaOH and CaO treatments. Untreated straw showed relatively less fungal colonization compared with treated straws being heavily colonized by rhizo ids and thalli. AHP-treated straw was most extensively colonized with rhizo ids observed penetrating deep into straw tissues particularly the bundle sh eath cells. The thalli of this study resembled mono- and poly-centric gener a of anaerobic Chytridiomycete fungi. The pattern of fungal colonization co mpared well with the previous degradability data on treated straws which de monstrates the value of such treatments to improve degradation of fibrous s ubstrates by rumen microorganisms, particularly fungi. (C) 2000 Academic Pr ess.