The experiment was carried out on 1440 broiler chickens assigned to 6 groups and lasted 8 weeks. The analyzed factors were breeding lines (Starbro and Vedetta) and rape seed varieties (Leo and Mar). The chickens in the experimental groups were fed 5% rape seed in their diets. At the age of 8 weeks the Starbro chickens that were given both rape varieties showed higher (P≤0.01) body weight gains and consumed less feed than Vedetta chickens. The latter line, however, had a much better carcass yield (P≤0.01) than Starbro. The thyroids of the experimental chickens from both lines were about 40% heavier than of controls. Feeding both varieties of rape seeds in the diets increased the femoral calcium content in both lines.