Transfer of lipid-soluble pesticides from contaminated feed to livestock, and residue management

Managing residues of pesticides in livestock requires information on likely residues in the livestock consuming treated or contaminated feed. Simple tools are required by those persons profiling risks to trade in animal commodities in order to screen the large number of chemicals and identify those that require further investigation and/or management strategies to be implemented. A simple model for simulation of residues of lipophilic xenobiotics in growing pigs, cattle and sheep is presented. This model provides pragmatic reasonable upper bound estimates of residues of lipophilic compounds in fat using minimal inputs such as: elimination half-life, fraction absorbed from the diet and, in the case of lactating animals, the ratio of the concentration of pesticide in milk to the concentration in body fat. These estimates from the model can be used in the first tiers of risk assessment, and/or to guide discussions on the management of livestock exposure to pesticides through feed.