The Effect of Feeding Alfalfa Hay Containing DDT Residue on the DDT Content of Cow's Milk

Summary 1. Alfalfa treated with 2.4 lb. of DDT per acre, in the form of an aerosol, and fed to cows at the rate of 1 lb. of hay per day per 100 lb. of body weight produced milk containing up to 10.1 γ of DDT per g. or 259.1 γ per g. of butterfat. The daily intake of DDT was as high as 903 mg. and the output in the milk was as high as 265 mg. 2. Alfalfa treated with 0.6 lb. of DDT per acre and fed to cows at the rate of 1.5 lb. of hay per 100 lb. of body weight produced milk containing up to 0.9 γ of DDT per g. 3. The output of DDT in the milk varied from 5 to 30 per cent of the intake. The DDT appeared in the milk after a very few days of feeding, and in one case was present in appreciable quantities after 3 days of feeding. 4. After the feeding of DDT hay was discontinued, DDT was detected in the milk for 160 to 170 days when large quantities of DDT had been fed and for only 30 to 40 days when small quantities had been fed.