Straw components of 14 wheat, oat and barley cultivars grown at four locations, 1975–1976, were compared for feed quality attributes before and after ammoniation. Based on a combined statistical analysis, significant differences (P < 0.05) among cultivars occurred among and within crops for crude protein (CP), in vitro digestible organic matter (DOM) and crude fibre (CF) for untreated straw residues. Average CP and DOM levels were lowest for wheat (3.6 and 36.7%, respectively). Barley had the highest average CP (4.9%) and oats the highest average DOM (39.8%). Wheat straw had substantially higher average CF than either oats or barley. Straw from Pitic 62 wheat, Random oats and Fergus barley showed superior quality attributes (high DOM and CP, low CF) for their respective crops. Neepawa wheat straw appeared to have the poorest quality overall. The straws were treated with anhydrous ammonia (5% on a wt/DM basis) and left in a sealed container at 20° and 15% moisture for 6 days. Following ammoniation: all wheat cultivars had higher CP levels than the oat and barley cultivars; average improvements in CP for wheat, oats and barley were 8.1, 4.7 and 5.3 percentage units, respectively; average DOM levels were similar for wheat, oats and barley; average improvements in DOM were 8.6, 6.1 and 6.6 percentage units, respectively. Neepawa had significantly higher CP following ammoniation than the oat or barley cultivars and showed the highest improvement in DOM (10.1 percentage units). Based on DOM values of the wheat, oat and barley straws, the cultivars Pitic 62, Random and Fergus would still be preferred after ammoniation. There was little to choose between several cultivars within crops for CP content after treatment with ammonia.