This experiment was conducted to evaluate the growth performance and carcass yield of Arsi-Bale sheep fed on lentil straw with concentrate supplementation. The dietary treatments were: lentil straw with concentrate supplement at 250 (T1), 300 (T2), 350 (T3), 400(T4) and 450 (T5) g lamb/day. Thirty-five yearlings Arsi-Bale lambs with initial body weight of 20.8±1.5 kg (mean ± SE) was randomly allotted to the treatments in randomized complete block design. The concentrate levels had significant (P< 0.05) effect on total DM intake with higher value in T3 (791.1), T4 (782.6) and T5 (826 g) than T1 (720.2) and T2 (735g) groups. The highest (P< 0.001) average daily live weight gain was attained by lambs in T4 (78 g) and T5 (84g). Feed conversion efficiency increased (P< 0.001) with increase in the concentrate amount. Lambs supplemented 350, 400 and 450g concentrate had higher (P< 0.05) carcass weight (10.6-11.4 kg) than those supplemented 250 and 300g concentrate. The dressing percentage (42%) observed for T4 and T5 lambs was higher (P< 0.05) than the other groups (37.9-40.1%). The feed cost (birr/kg gain) in T1 (111) and T2 (97), were higher (P< 0.001) than that of other treatments (67-80 birr/kg gain). It can be concluded that 400-450g of concentrate is the optimum level, for improved feed consumption, live weight gain, FCE, feed cost per unit of live weight gain and carcass yield of Arsi-Bale sheep fed on lentil straw as roughage source.
