| The aim of this study was to determine the duration of the resistance after the end of the ingestion of non-toxic doses of Crotalaria retusa seeds. Ten sheep were divided into 3 groups of 3 animals each and a control group with 1 sheep. To induce resistance, sheep in groups 1, 2 and 3 received 20 daily doses of 2g kg-1 of C. retusa seeds, followed by 7 daily doses of 4g kg-1. To determine the duration of resistance the sheep in groups 1, 2 and 3 were challenged orally, 3, 7 and 15 days, respectively, after receiving the last dose of 4g kg-1, with a single dose of 5g kg-1. Sheep of groups 1 and 2 did not develop overt signs of poisoning. Two sheep of group 3, challenged 15 days after the end of the resistance induction period, showed signs of acute... |
