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Secretion of DDT by Lactating Cows Fed Thyroprotein^1,2

Department of Dairy Science

J. M. Witt³

Department of Entomology, The University of Arizona, Tucson

ABSTRACT

Six lactating cows were subjected to DDT [2,2-bis (p-chlorophenyl) -1, 1, 1-trichloroethane] contamination by intravenous dosing at a rate equivalent to 4 ppm dietary intake for 14 consecutive days. Following a ten-day decline period, three animals were given a thyroid active substance⁴ at the rate of 1 g/11 kg body weight for 28 consecutive days. The DDT output in the milk of the control arid thyroproteindosed animals was followed for 58 days after the prescribed dosing. Milk and milk fat yield increased and body weight decreased in the animals receiving thyroprotein. These yield figures declined below the values in the control group after thyroprotein feeding ceased. Concentration of DDT in the milk rose during intravenous administration to an average of 30 ppm and declined to about 7 ppm for both groups prior to thyroprotein feeding. The pesticide content of the milk fat of the control animals declined steadily to 2 ppm during the remaining 12 weeks of the ex- periment. The DDT level in the milk of the animals that received thyroprotein declined to only about 4 ppm during the comparable time. When the milk pesticide was expressed in terms of mg excreted per day, the thyroprotein-fed animals had a 2 mg/day higher yield during the thyroprotein dosing period. One week after the end of thyroprotein feeding the yield level had assumed almost identical values in both groups of animals.

¹ Arizona Agricultural Experiment Station, Technical Paper no. 1253.

² Supported in part by Grant no. EF-00627-02 from the USPHS and by a grant from the United Dairymen of Arizona.

³ Present address: Dept. of Agr. Chem., Oregon State University, Corvallis, Oregon.