Forty-eight 4-week-old White Rock growing chickens (mean live weight 500 (s.e. 9·3) g) were given, by crop intubation, four isoencrgetic (13·1 M] metabolizable energy (ME) per kg dry matter (DM)) and isonitrogenous (120 g crude protein (CP) per kg DM) semisynthetic diets based on vetch (V) or bitter vetch (B) seeds, untreated or antoclaved at 120°C for 30 ruin (diets V, AV, B and AB, respectively). Autoclaving of the seeds caused some changes in amino acid (AA) composition but did not reduce the availability of A As, especially of lysine.
The average apparent AA digestibility values derived from ileal content were 0·75, 0·85, 0·59 and 0·85 for diets V, AV, B and AB, respectively, corresponding to true absorption values of 0·90, 1·00, 0·74 and 0·97, respectively. Although the apparent digestibility values of several AAs were relatively low (methionine, isoleucine, tyrosine and cystine), most were higher than 0·70. Heat treatment resulted in a significant increase (P < 0·05) in the AA apparent digestibility of both seeds. It is concluded that heat treatment is useful for improvement of vetch and bitter vetch seeds for inclusion in poultry diets.