Bioconversion of agro-residues, rice straw and wheat straw, was carried out with the edible mushroom Pleurotus sajor-caju, with a view to increasing nutritive values and digestibilities for animal feed. Amongst the inorganic and organic nitrogen sources tested, soyabean meal and ficus fruits, in which nitrogen is present in complex form, were the best supplements in enhancing the in vitro dry matter digestibilities of the residues. (C) 1997 Elsevier Science Ltd.