Lactational Output of DDT Fed Prepartum to Dairy Cattle

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Abstract
Dry dairy cows and heifers approaching their first lactation were fed l,l,l-TRICHLORO-2,2-B!S(41-CHLOROPHENYL) Ethane (DDT) from the 90th to the 30th day before expected parturition. A control and 3 treatment groups of 4 animals each were used. Feed contamination levels of 30, 300, and 600 ppm were approximated; mean total intakes of crystalline DDT were 28, 250, and 520 g/cow for the treated groups. No gross signs of toxicity were observed. Body fat DDT concentrations rose to 16, 253, and 590 ppm in the treated groups. Concentrations fell after cessation of intake at rates of 8 to 10%/week. Maximum milk fat DDT concentrations after calving were 19, 231, and 812 ppm for the treated groups, respectively, and declined through the lactation at from 9 to 11%/week. The DDT level in the milk fat of the cows with lowest intake did not reach 1 ppm until after 17 to 26 weeks of lactation. Therefore, giving dry cows or heifers feed contaminated at or above this level is impractical, even if the feed is withdrawn z month before calving. Whole blood levels of DDT, determined twice during the experiment, were closely associated with body stores of SST, particularly in the animals fed at the 2 higher levels of the insecticide.