An experiment was carried out at Debre-Zeit Agricultural Research Center to evaluate the performance of yearling Arsi-Bale lambs fed desho grass hay as a basal diet ad-libitum with and without supplementing concentrate mixture. Growth performance of the lambs was evaluated using desho grass hay ad libtum alone (T1) and supplemented with different concentrate mixture; 200 (T2), 300 (T3) and 400g (T4) head-1. Twenty-four yearling intact lambs with an initial body weight of 20.7±1.50 (mean ± SE) were randomly allotted in to six groups of 4 animals per group and assigned to four treatments in randomized complete block design. Dry matter intake of lambs recorded in T4 (825 g) was higher (P≤ 0.001) than in T3 (732 g), T2 (681 g) and T1 (456 g) groups. Animals in 400g concentrate supplementation (T4) had higher (P≤ 0.001) daily average weight gain (97 g), carcass yield (11.7 kg), dressing percentage (42%), and lower feed conversion ratio (8 g feed /g gain) than in T1 and other supplemented groups. It could be concluded that supplementation with 400 g concentrate (T4) h-1, d-1 was found to be an optimum level of concentrate diet to support greater weight gain, carcass yield and lower feed conversion ratio.
