Residues of DDT and dieldrin in the subcutaneous fat and butterfat of cattle

Abstract

Technical DDT or dieldrin was added to crushed wheat and fed to steers and dairy cows. Subcutaneous fat collected by biopsy and butterfat were examined for residues of DDT, DDD, DDE and dieldrin. Steers fed 6, 36 or 216 mg DDT/day for 10 weeks had total DDT residues (mean ¦ s.e.) in subcutaneous fat of 0.38¦ 0.01, 2.72¦0.37 and 24.5¦6.9 mg/kg respectively. DDD was the major residue, comprising 80% of the total. When DDT was withdrawn from the diet, residues declined. Half-life for DDT was 11 weeks (range 8-14), and for DDD was 5 weeks (range 3.5-7.4). Half-life could not be determined for DDE. Steers fed 36 mg dieldrin/day for 10 weeks had 17.3¦4.9 mg/kg dieldrin in the subcutaneous fat. The half-life for dieldrin was 5 weeks (range 2.5-10.0). Dairy cows fed 6, 36 or 216 mg DDT/day for 6 weeks had total DDT residues in butterfat of 0.31¦0.05, 2.5¦0.60 and 20.8¦1.2 mg/kg respectively. DDD was again the major residue, comprising 65% of total residues. Half-lives of DDT, DDD and DDE in butterfat were 7.2 (range 6.3-7.7), 3 (range 2.2-3.0) and 5 weeks (range 3.5-8.0) respectively. When 36 mg dieldrin was fed to dairy cows for 6 weeks, residues of 17.3¦4.6 mg/kg were found in the butterfat. The half-life for dieldrin in butterfat was 9 weeks (range 6-11.5).