Feed mixtures containing different amounts of untreated and NaOH - treated wheat strau were fed to young bulls. The wheat strau was treated with 4.5 kg NaOH on 100 kg straw (dry matter basis). For the feed mixtures containing up to 40% (5, 20, 40%) untreated and NaOH - treated straw coefficients of digestibility were not significantly different. The feed mixtures containing above 40% NaOH - treated straw (50%) showed the improvement of digestibility by 4 to 7 units.