Growing fattening bulls in Belgium require diets high in concentrate and low in roughages in order to achieve large live weight gains and high quality carcasses. Sugar beet pulp is usually incorporated at a high inclusion rate in fattening diets. It is supplemented with cereals, by-products like wheat bran or glutenfeed and protein supplements very often of vegetable origin. The fat content of such diet is low. Over the recent years, there has been an increasing pressure from the industry to incorporate fat in fattening diets. Each company produces its own fat concentrate. They are blends of various origins. The present experiments were carried out to assess the effects, on animal performances, of soya oil and linseed, two fat concentrates of vegetable origin incorporated in fattening diets.