This study was conducted to study the effects of different sources of low starch by-products substituted for barley grain on in situ rumen degradability and in vitro gas production properties of a total mixed ration. The experimental treatments consisted of 370 g/kg roughages and 630 g/kg concentrates. The total mixed diets contained 100 g /kg dry matter (DM) barley grains (BG, control diet), sugar beet pulp (SBP, treatment 2), wheat bran (WB, treatments 3), or dried citrus pulp (DCP, treatment 4). In the first experiment, the experimental diets were evaluated for in-situ rumen degradability by the nylon bag technique. In the second experiment, treatments were evaluated for in vitro gas production parameters. Data were analyzed as a completely randomized design. The data on in situ experiment indicated that non-soluble degradation fraction (b), the fractional degradation rate (c) and potential degradability (a+b) were not affected by the diets (P>0.05). However, soluble degradable fraction (a) was highest for a diet with DCP (P<0.05). The in vitro gas production data showed there were no significant differences among treatments for gas produced at different times of incubation (P>0.05). Besides, the potential gas production (b), and OMD did not differ among treatments (P>0.05). But, the fractional rate of gas production (c) was lowest for diet with DCP (P<0.05). Still, SCFA varied among various treatments (P<0.05), and it was higher for DCP treatment than other groups. It concluded that replacing low starch by-products, such as dried citrus pulp and sugar beet pulp, for up to 10% of diet DM instead of barley grain can improve the DM digestibility of a total mixed ration without any adverse effect on ruminal fermentation in ruminants.

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