The study was conducted to determine growth performance, reproductive development, and seminal plasma biochemical profiles of Fleckvieh bull cattle, supplemented with diets differing in protein sources: yellow lupine (Lupinus luteus cv Salut), white lupine (Lupinus albus cv Amiga) and rapeseed. The average daily feed intake as well as feeding behaviours (total number and duration of visits in the feeding trough) did not differ among the diets (p>0.05). However, there was a significant decrease in average daily gain and increased the feed conversion ratio throughout the whole feeding trials of bulls fed with yellow and white lupine diets.