The effect of grounded barley grain (BG), as a silage additive, on chemical composition, qualitative properties, in situ dry matter (DM) degradability and in vitro gas production of citrus pulp silage (CPS) was investigated. The whole fresh citrus pulp was manually chopped and used as either untreated or treated with 6, 12, or 18 g BG.kg-1 fresh citrus pulp for ensiling. The data were analyzed in a completely randomized design. The data showed that the silage with 18 g BG had highest DM and CP content among the treatments (P < 0.05). Also, with increasing of BG, the NDF and ADF concentrations linearly increased, but pH linearly decreased (P < 0.05). Aerobic stability of silages exhibited a negative relationship with adding of BG (P < 0.05). Data on in situ degradability of DM indicated that the soluble degradable fraction (a) was highest in control group (P < 0.05). Besides, the non-soluble degradation fraction (b) was highest in silages with BG (P < 0.05). The fractional degradation rate (c) linearly increased with increasing of BG (P < 0.05). After that, the potential DM degradability (a + b) was lowest in the treatment with 18 g of BG (P < 0.05). But, the effective degradability (ED) of DM was highest in treatments with BG (P < 0.05). The data on gas production test indicated that the potential (b) and fractional rate of gas production (c) was highest in silages with 12 and 18 g of BG (P < 0.05). Furthermore, treatments with 12 and 18 g of BG had higher OMD, NEl , ME and SCFA contents than other treatments (P < 0.05). This data suggest that the addition of 12 and 18 g of BG to CPS can improve the nutritional value of this by-product.

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