Seeds of the plant Crotalaria retusa L., containing 4·4% of the pyrrolizidine alkaloid monocrotaline, were fed in a finely ground form to broiler chickens at 0·005, 0·01, 0·05, 0·10 and 0·50% by weight of the diet continuously for 8 weeks.
Feeding 0·005% and 0·01% had no effect on the growth performance of the birds. A non-significant reduction in live-weight gain, one death and chronic disease resulted from feeding 0·05%. At 0·10% and 0·50% there was high mortality and reduced voluntary feed intake, live-weight gain and feed conversion efficiency, the severity of the response being greater at 0·50%.
Feather development was inhibited in birds fed 0·10% and 0·50% C. retusa seed.
Until further research is done to determine the effect of feeding between 0·01% and 0·05% ground C. retusa seed in the diet of broiler chickens, it is suggested that the maximum should be 0·01%.