Organochlorine Residues in Pasture and Livestock

The occurrence and persistence of OC residues in both animal fat and in soil is reviewed. These chemicals have caused problems in production of pasture and grain for livestock. Management strategies to give short term guidelines to graziers are described. Attempts to increase the rate of breakdown in the soil under Australian conditions by varying frequency of cultivation, by addition of lime or nitram, by weekly irrigation or by combinations of these have been unsuccessful. Deep ploughing to 500 mm has reduced residues of heptachlor and chlordane by 35-52% in soil. Other Australian work has examined the uptake of OCs by pasture plants in the field and in the glasshouse, for both summer and winter species. It was found that the seedling stage of plant growth contains the highest residues with almost nothing present at maturity. Species selection could be utilized to minimise residues.