1. The applicability of different ratios of bitter vetch seed as a new method for moult induction in laying hens was studied. The effectiveness of bitter vetch seed on post-moult production and post-moult egg quality was also investigated. 2. A total of 120 Single Comb White Leghorn hens, 78 weeks of age, were used in this study. The hens were randomly assigned to 5 treatment groups of 24 birds each. The treatments were 30% bitter vetch seed (BV30) diet, 60% bitter vetch seed (BV60) diet, 90% bitter vetch seed (90BV) diet, feed withdrawal method (FW) and full-fed non-moulted control (CON). 3. Egg production ceased first in FW and BV90 treated hens and last in BV30 treated hens. As the percentage of bitter vetch seed increased in the moulting ration, feed intake decreased and body weight loss increased during the 10-d moult induction period. Time to first egg production was significantly greater in hens exposed to the FW and BV90 diets. 4. FW and BV90 treatment hens had significantly higher hen-d egg production than non-moulted control hens. Egg weight was significantly higher in BV30 and BV90 treatments. There were no differences in egg mass, feed intake and mortality among experimental treatments during the post-moult period. 5. No significant improvements were observed in exterior or interior egg quality in moulted hens, except for Haugh units, which were significantly higher in moulted hens when compared to the non-moulted control hens. 6. In conclusion, the present study showed ad libitum feeding of a layer ration with 90% of bitter vetch seed for 10 d proved to be effective for inducing moult, increasing post-moult egg production and improving some internal egg quality parameters
