Results of the in vitro technique revealed that alkali treating of WBG caused an increase in the gas volume at t1/2 but was not significant (P<0.05). Apparent substrate degradability (ASD) and true substrate degradability of barley grain (TSD) increased by NaOH-treated barley versus untreated barley which may originate from reducing the resistance of seed coat by treatment. This confirmed the findings of Ørskov et al.(1981) who reported that for whole barley, the digestibility of all fractions improved by treatment with NaOH. In addition, Barnes and Ørskov (1981) indicated that the digestibility of starch increased linearly with NaOH application. Rumen microbial-N yield decreased (from 1.344 to 1.282 mg) by the treatment of barley with NaOH. The finding of present study leads us to conclude that treatment of WBG with sodium hydroxide had no effects on substrate degradability and microbial-N production.

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