The chemical composition and nutritional value of yellow (Juno and Popiel), blue (Emir and Sur) and white (Wat and Bardo) Polish sweet lupin varieties were compared. The effects of enzyme preparations, Energex and Bio-Feed Plus, on the hydrolysis of the seed components in vitro and of Energex and Alpha-Gal on the nutritional value of lupin for broiler chickens, were evaluated. The protein content was the highest in the yellow lupins (44%), while that of fat in the white (9%). The alkaloid content ranged from 0.23 to 1.3 g/kg DM . The metabolizable energy (AME_N) as determined on 4-week old chicks, was the highest in Bardo, the lowest in Emir (11.2 and 8.4 MJ/kg DM, respectively). The apparent protein and fat digestibility of lupins determined on 4-week old chicks did not differ among cultivars and averaged 84 and 73%, respectively. Relatively large differences in digestibility of carbohydrate fractions were noted among cultivars (e.g. NFE from 0 to 23.9%; CF from 0 to 20%). The growth performance of broiler chicks fed between day 8-29 of life on isoprotein and isocaloric diets containing 15 and 30% lupin was determined. At the 15% inclusion level only Wat significantly lowered performance indices, however, at the 30% level these indices decreased significantly for all cultivars except Bardo. In vitro, Energex increased the degree of hydrolysis of NDF and ADF in Wat by 19 and 10%, respectively, and increased the solubility of protein of all lupin cultivars by 12%, on average. In vitro Energex increased the AME_N value of Juno, Emir, Sur and Wat by about 1.5 MJ/kg DM and Alpha-Gal acted only on blue lupins (1.6 MJ/kg DM). However, supplementation of diets containing 23% of Juno and Emir seeds with 0.1% of Energex or Alpha-Gal did not improve the performance of the birds in a 3-week experiment.