Test No. 503: Metabolism in Livestock

Metabolism in Livestock studies are used to determine the qualitative and quantitative metabolism and/or degradation of the active ingredient resulting from pesticide use in feedstuffs, direct application to livestock, or premise treatment. The studies provide an estimate of total residues in the edible livestock commodities, as well as the excreta; identify the major components of the terminal residue in the edible tissues; elucidate a metabolic pathway for the pesticide in ruminants and poultry; provide evidence whether or not a residue should be classified as fat soluble. The studies should be conducted using radiolabelled test compound. A stable position of labelling is chosen and the preferred radioisotope is 14C, although 32P, 35S can be used. A ruminant (lactating goats) study can be carried out on a single animal per experiments. For poultry (laying hens), the use of ten birds per experiments (or dose) is recommended. The minimum dosage used in livestock oral metabolism studies should approximate the level of exposure expected from the feeding of treated crops with the highest observed residues. Treatment should be administered orally (via a balling gun, capsule or gavage) or by dermal application. The study includes: the excreta, milk and eggs collect (twice daily), and tissues collect (muscle, liver…).