Effects of Rabaa (Trianthema pentandra L.) ash alkali on sesame straw (Sesamum indicum L.) chemical composition and artificial fibre bags degradation in the rumen of three Nubian goats fed groundnut haulm were studied. The straw was treated with 0, 3, 5 and 8% Rabaa ash alkali forming diets USE, AT1SE, AT2SE and AT3SE, respectively. The alkali affected the chemical composition by decreasing CF (40.01, 32.43, 34.94 and 34.92) and EE (1.40, 1.09, 0.96 and 1.08) and increased CP (4.52, 5.74, 5.80 and 4.94) and ash (7.84, 13.30, 14.67 and 19.63) for diets USE, AT1SE, AT2SE and AT3SE, respectively. Increasing alkali level significantly increased ash and generally decreased CF and NFE. Increasing the alkali level had generally increased DM and OM degradation at 6, 12, 24 and 72 h. It also increased OM degradation at 6 and 72 h. Increase alkali level had increased DM, OM and CP degradation characteristics including the soluble fraction, the fraction degraded with time and total degradation. Hence it is concluded that Rabaa ash alkali treatment of straw will improve the quality of the sesame straw which could be adopted by farmers.