The effect of dipping on the incidence of DDT in dairy products

Abstract

The DDT content of milk, cream, and factory butter from cattle dipped fortnightly in 0.5 per cent DDT baths for the control and attempted eradication of the cattle tick Boophilus microplus (Can.) has been measured. Contamination of milk under control conditions was higher than that reported by others using comparable spraying techniques. This is ascribed either to the generally greater thoroughness of the dipping technique in applying DDT to animals or to the greater deposition and penetration of DDT taking place with the particular formulations used. Successive dippings over a period of 15 months under eradication conditions caused much higher contamination, and DDT residues persisted in butter for at least nine months after dipping stopped. DDT storage in animal body fat was favoured by lowered butterfat production, but most of the stored DDT was excreted when butterfat production rose again.