In many regions, ammoniation of straw is hindered by the cost or non-availability of anhydrous or aqueous ammonia and by poor upgrading responses with urea. Ammonium salts constitute a safe, alternative source of ammonia. In vitro studies have shown that ammonia produced by heating ammonium ‘carbonate’ (mixture of the carbamate and bicarbonate) or bicarbonate to 90°C for 15 h with water produced improvements in the digestibility of straw which were similar to those achieved with aqueous ammonia. Under identical conditions ammonium sulphate gave a similar response only when reacted with a stoichiometric excess of quicklime (CaO) or slaked lime (Ca(OH)2 ) and water to produce ammonia. When the straw was treated at 20°C for 35 d, upgrading was achieved only when the volatile or non-volatile ammonium salts were mixed with an excess of CaO or Ca(OH)2 plus water.