The effect of substitution of soyabean oilmeal with evening primrose (Onothera paradoxa) oil cake was investigated on 60 bull calves from days 7 to 120 of age, divided into three groups: control, C, fed with soyabean oilmeal as the main source of protein in the concentrate mixture; P1, 50% soyabean oilmeal protein was substituted with the equivalent of evening primrose oil cake; P2, total protein of soyabean meal was substituted with protein of evening primrose oil cake. In the respective diets, the feed mixtures contained 0, 16.5 or 33% of evening primrose oil cake. The calves were given about 350 kg of whole milk from days 7 to 56 of life. The increased level of evening primrose cake in the diet augmented feed intake but was not reflected in body gains (P>0.05), and significantly decreased feed efficiency (P<0.01).