Twelve male Friesian steers with average body weight 269+ 9 kg and 15 month of age were used in this study. Steers were distributed into three groups similar in number. The experimental rations were formulated as follows: ration 1 (R1) 81.8% concentrate feed mixture (CFM) + 18.2% clover hay (CH) (control), ration 2 (R2): 81.55% CFM + 18.05% CH + 0.40% seaweed (S) and ration 3 (R3): 81.23% CFM + 17.87% CH + 0.90% S. The results obtained showed that the mean values of blood parameters were not significantly affected by the feeding on R1 or R2 or R3. The concentration of urea–N in blood was decreased with feeding on R2 and R3 than feeding on R1. The average daily gains were 0.81, 1.00 and 0.83 kg/d for steers fed on R1, R2 and R3, respectively. The production efficiency was higher when feeding on R2 (24.04 %) than feeding on R1 or R3 (20.97 and 19.17%, respectively), and the economic efficiency, was higher when feeding on R2 (25.39 %) than feeding on R1 or R3 (13.3 and 3.94 %, respectively). In general, the results indicated that feeding ration at a level 81.55% CFM + 18.05% CH + 0.4% S for fattening Friesian steers was economically improved animal performance compared with the other two rations.