Metabolism of TOK Herbicide in the Dairy Cow

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Abstract
TOK (2, 4-dichloro-4[image] -nitrodiphenyl ether), a selective herbicide for weed control in alfalfa, corn, and other crops, was fed to a lactating dairy cow to study its metabolic fate. No residues of TOK were found in the milk, urine or feces of a cow fed 5 ppm of the herbicide in its feed. TOK readily disappeared in the presence of fresh rumen fluid in vitro as determined by electron affinity gas chromatography. A metabolite was rapidly produced in the rumen fluid which had a retention time identical with that of the nitro reduction product of TOK, 2, 4-dichloro-4[image] aminodiphenyl ether, (amino-TOK). This metabolite was absent in the chromatograms of milk, urine and feces.