The distribution, live sampling for and decline of DDT in steers

Abstract

Following DDT contamination of steers grazing pastures polluted by spray-drift from nearby crops in the Ord Valley of Western Australia, experiments were conducted to determine: 1, the distribution of DDT and metabolites (referred to hereafter as DDT) within the carcase fat tissues; 2. a suitable method of sampling fat from live steers; 3. the rate of decline under local feeding conditions with maintenance feeding for 201 days and with ad lib feeding for a further 156 days. There was no significant difference between the DDT concentrations found in the renal, omental, subcutaneous and scrotal fat. A method of sampling fat from the scrotum permitted repeated sampling of steers in good condition at an operation rate of 15 animals per hour. DDT was lost at a mean rate of 0.0031 log mg kg-1 DDT day-1 during the maintenance feeding period despite a level of 1.5 mg kg-1 DDT in the feed. During the ad lib feeding period the loss was 0.0014 log mg, kg-1 DDT day-1. The distribution of DDT values in the experimental herd was skewed; the implications of this on the amount of sampling necessary to ensure that no animal in a group will exceed minimal accepted values of DDT are discussed.