Principles of a full 'relay toxicity' experiment and results conducted with carbadox, a feed additive used as growth promoter for growing swine.

Relay toxicity is a new approach which permits an evaluation of the harmlessness of residues found in tissue, for the human consumer. Farm animals, swine for example, received high quantities of the additive over a long period. The swine were sacrificed without any withdrawal. Their meat and liver were added to the feed ration of laboratory animals to study the eventual problems of residue and metabolites. The following experiments were performed using carbadox:--Levels of carbadox up to 200 ppm were added to the swine ration (a maximum of 20 ppm is authorized). The meat and dehydrated liver were given in doses of 20% and 10% respectively, in the rat feed for 2 years or 3 generations.--The fresh meat, frozen then thawed at the time of use, was distributed to dogs daily for 7 1/2 years. No abnormalities were found, either in the growth of the animals or in their descendants. No abnormalities were observed macroscopically or microscopically after sacrifice. Relay toxicity gives high coefficients of security when the additive is used without withdrawal up to the time of sacrifice. This study demonstrated that the use of carbadox in swine doesn't present any disadvantage to the human consumer.