Five Ossimi and five Merino rams were housed in semi-open pen with yard shaded. The animals were fed concentrate feed mixture (CFM) at the rate 1.5% of their live body weight (LBW) plus green berseem ad-libitum during the coldest (8.3+0.3 ^oC) winter months (December-January). While during the hottest (29.7+0.1 ^oC) summer months (July-August), animals were also fed CFM at the rate 1.5% of their LBW plus berseem hay ad-libtium. Metabolism trials were conducted (two trials in each season) with the two breds (Ossimi and Merino sheep), using 3 rams from each breed fed on winter and summer rations. Digestibility of all nutrients and feeding values of winter ration were higher (P<0.05) with Merino than Ossimi rams, the opposite trend was noted in summer ration. The daily DM and feed unit intakes were higher in winter than summer.  Water intake increased in summer to more than double of that in winter with both breeds. Urine output in both breeds was higher in summer than in winter. The anions (Cl^- and  P^---) and cations (Na⁺ and K⁺) in blood serum of both breed were almost similar under cold winter or hot summer months. The results showed clearly that there were significant differences between the tested breeds in winter and summer seasons concerning feeding values, daily intake and water balance.