Secretion of DDT in Milk

Abstract

Environmental contamination of animal feed by pesticides applied onto nearby crops is considered to be the major source of pesticide residues found in milk. However, examination of the pesticide input from these sources frequently does not account for the level of pesticide residue found in the corresponding milk. Attempts to explain the discrepancy between the amount of pesticide residue found in milk and the amount which one can predict should be found based on many feeding studies (1, 2, 3, 4) has led many persons to suggest that there may be a relationship between these unexplainably high pesticide residues in milk and the stage of lactation in the cow, i.e. that cows which have just come fresh secrete more pesticide in their milk fat than during later stages of lactation. The rationale which prompted this suggestion is based on the fact that a cow loses considerable body weight, presumably stored body fat, during the first weeks following parturition. Since cows store insecticide in their body fat at a level near that secreted in the fat of milk (1, 2, 5, 6) it appeared reasonable that depletion of body fat would release the previously stored insecticide and make an unusually large amount of insecticide available for secretion in the milk.

1 Arizona Agricultural Experiment Station Technical Paper No. 1078

2 This work was supported in part by Grant No. EF-00627–01 from the U.S.P.H. and a Grant from the United Dairymen of Arizona and The Arizona Federated Milk Producers.