Two groups (n=30) of crossbred lambs (25% Polish Merino, 25% Booroola and 50% Suffolk) were intensively fattened from the age of 8 weeks until reaching a body weight of 35 kg. Group II received a pelleted concentrate containing 207 g of crude protein (CP)/kg of dry matter (DM) and 12.5 MJ of metabolizable energy (ME)/kg DM and group I was fed a concentrate with a similar nutritional value (202 g CP/kg DM and 12.7 MJ ME/kg DM) but soyabean oilmeal and dried sugar beet pulp were substituted by solvent-extracted rapeseed oilmeal (25% in mixture) and oats, respectively Lambs of both groups consumed a similar quantity of DM, CP and ME (respectively 85 g, 17 g and 1.1 MJ/kg W^0.75 and 77 g, 16 g and 1.0 MJ/kg W^0.75 for group I and II), irrespective of the type of concentrate offered. Daily weight gains of lambs from group I (290 g) were lower (P<0.05) than those of lambs from group II (325 g). No significant differences between groups were observed in the intake of CP or ME per kg of weight gain (group I - 649 g and 40.8 MJ and group II - 595 g and 35.9 MJ). The cost of concentrate used for the production of 1 kg of liveweight was similar in both groups.