Ddt residues on pasture and in the butter-fat of cows grazing pasture treated with ddt prills and ddt/superphosphate

Abstract
DDT was determined in the butterfat of cows grazed on pasture at various intervals after it had been top-dressed with either DDT priUs or DDT/superphosphate dust, each at a nominal rate of 2 lb pp′-DDT/ac. Approximately five times less DDT was found in the butterfat of cows grazed on the prill-treated areas, and this corresponded to the lower degree of pasture contamination from the use of DDT prills. Data are presented on the correlation between DDT residues on pasture and in butterfat, the influence of formulation of DDT on the length of withholding periods for lactating cows and on the rate of decontamination of dairy cows, having DDT in the body fat, when removed to DDT-free pasture.