Metabolism of Daconil and Dacthal Pesticides in Lactating Cows

Abstract

Daconil (tetrachloroisophthalonitrile) fungicide and Dacthal (dimethyl-2,3,5,6-tetrachloroterephthalate) herbicide are effective agricultural chemicals on a wide variety of crops, including forage. In the work reported, the fate of these compounds was studied in dairy cows. No residues of these compounds were found in the milk. No residues of intact Daconil were found in the manure or urine. Daconil rapidly decomposed in fresh rumen contents with the production of 2 unidentified metabolites. One per cent of intact Dacthal was found in the manure. The hydrolyzed metabolite, l-methyl-4-carboxyl-2,3,5,6-tetrachloroterephthalate (Dacthal monoacid), was eliminated in the manure and urine to the extent of 3.3 and 90.9%, respectively. This same metabolite was rapidly produced from Dacthal incubated with beef liver slices. Dacthal did not decompose when incubated with rumen contents.