This study was conducted to determine the effect of combining rice bran and rice husk as a substitute ingredient in maize straw silage-based rations on rumen fermentability. The study used a completely randomised design with different proportions of rice husks as a factor. Rice husk was a replacement for rice bran at levels of 0, 10, 20, 30, and 40% in a maize straw silage-based ration (dry matter (DM)). The forage-to-concentrate ratio was 60:40. Measurements included pH, ammonia, total volatile fatty acids, partial, methane and total gas production, conducted after 24 h of incubation, while dry matter digestibility and organic matter digestibility were measured after 48 h of incubation. Data were analysed using one-way ANOVA. The results showed that incrementing rice husk levels in the ration significantly reduced (P < 0.01) its quality. Fermentability, digestibility, total gas and methane production decreased linearly (P < 0.01) with increasing rice husk content. Our findings imply that the addition of rice husks (DM basis) to the ration should not exceed 20%, or the substitution of rice bran with rice husk should not exceed 50%.