Milk Contamination From Low Levels of DDT In Dairy Rations

Abstract

Five groups of lactating cows were fed rations containing low levels of DDT for 26 wk. Mean DDT concentrations of the rations were 0.09, 0.24, 0.39, 0.73, and 0.28ppm. The first group served as control; solutions of crystalline DDT were added to the grain ration of the next three groups; and the 5th group received DDT from field-contaminated alfalfa hay. Maximum milk fat DDT concentrations determined by gas chromatography were 0.38, 0.45, 0.53, 0.92, and 0.53 for the groups of four, three, four, three, and four cows per group, respectively.An equilibrium point in milk fat DDT concentration was observed. Maximum values were reached at 18 to 21 wk, but fell slightly thereafter, although intake continued through 26 wk.The milk fat DDT concentration of cows fed field-contaminated forage did not differ significantly from that of cows receiving similar levels of supplemental DDT in their concentrate ration. It is concluded that lactating cows, continuously provided feed with a DDT concentration under 1.0ppm, will produce milk fat of a DDT concentration similar to that in their feed. The continual feeding of field-contaminated alfalfa hay containing 0.5ppm DDT will result in a milk fat concentration slightly above 0.5ppm but well below 1.0ppm.