Wpływ bobiku o wysokiej lub niskiej zawartości tanin na wyniki odchowu i wartość rzeźną kurcząt brojlerów. Część I. Wyniki odchowu i analizy rzeźnej kurcząt Summary. The aim of the study was to compare the effectiveness of the use of mixtures with different content of high-or low-tannin faba bean in chickens for fattening. The study was performed on 160 sexed broiler chickens, assigned to 5 groups of 32 birds each. For the first 21 days chickens were fed starter mixtures and grower mixtures for the following 14 days. The seeds of faba bean were the experimental factor introduced into the starter/grower mixtures, according to the system: group I -without faba bean, group II -8/15% of high-tannin faba bean seeds, group III -16/22% high-tannin faba been seeds, group IV -8/15% low-tannin faba been seeds, group V -16/22% low-tannin faba been seeds. It was shown that regardless of the variety and the percentage of faba bean seeds in starter/grower mixtures, chickens reached similar (1864-1925 g) final body weight gain with a similar (1.60-1.62 kg) feed conversion ratio. There was no effect of the applied feeding on carcass quality and muscle percentage in chickens' carcasses. However, introduction of faba bean to the mixtures significantly (P < 0.05) reduced chickens' fatness. The obtained results allow to recommend an even higher percentage of faba bean in mixtures, because it has not affected breeding results and significantly decreased fatness of broiler chickens.