RATE OF DECLINE OF CHLORFLUAZURON CONCENTRATION IN THE FAT OF CATTLE

Objective To determine the rate of decline of chlorfluazuron (CFZ) con centration in the fat of cattle. Design A field depletion study. Anima ls Fifteen steers that had become contaminated with CFZ through eating cotton trash or cotton leaf pellets derived from CFZ-treated cotton c rops. Procedure Fat samples were collected from the cattle al about 3 week intervals according to a schedule where each animal was sampled o n four occasions up to 340 days after removal from the contaminated fe ed source. Results When the effects or dilution are removed CFZ concen trations were found to decline slowly for about 200 days. Depletion wa s minimal between 200 and 340 days. Conclusion According to this trial , CFZ-contaminated, nonlactating cattle which have finished growing wi ll remain contaminated. Field experience has not supported this conclu sion.