One of the disadvantages in using field beans (Vicia faba) has been the presence of tannins which form insoluble complexes with proteins, enzymes and carbohydrates. This experiment evaluated zero-tannin, white-flowered varieties and tannin-containing, coloured-flowered ones, in terms of the utilization of energy and nitrogen by broiler chicks.

A basal diet was designed to give sub-optimal levels of protein (70% of requirement, ARC 1975). The 5 bean varieties were incorporated into the basal diet at 4 rates (Table 1). Three of these were white-flowered with negligible levels of tannin (Albinette, 0.006g/kg; Blandine, 0.005g/kg; and Albatross, 0.010g/kg) and two were coloured-flowered and contained significant levels of tannins (Minden, 0.138g/kg; and Alfred, 0.113g/kg). Methionine and lysine were subsequently added in quantities sufficient to ensure they were not first limiting. The 16 diets were fed to Cobb broiler cocks of 7 days initial age (4 replicates of 2 birds per cage).