The metabolism and residues of [14C]Endrin in lactating cows and laying hens

[14C]Endrin was fed to two lactating cows in a portion of their diet for 21 days. The intake was equivalent to approximately 0.1 mg of endrin per kg of total diet. Excretion of radioactivity in milk, urine and faeces reached equilibrium with intake between 4 and 9 days after starting treatment. Milk residues reached 0.003–0.006 mg/kg, were composed of unchanged endrin and were located in the fat. Muscle residues reached 0.001–0.002 mg/kg. Residues in the fat reached a maximum of 0.1 mg/kg and were due to unchanged endrin. [14C]Endrin was administered in corn oil to six laying hens for 21 weeks. The intake was equivalent to approximately 0.13 mg/kg of total diet. Ingestion and excretion were almost in balance at 16–20 weeks. Egg residues reached 0.11–0.18 mg/kg, were composed of unchanged endrin and were located in the yolk. Tissue residues were 0.01 mg/kg in breast, 0.1 mg/kg in leg, 0.17 mg/kg in kidney, 0.47 mg/kg in liver and 1.0 mg/kg in fat. The residues were accounted for as unchanged endrin except in liver and kidney in which part was probably due to polar metabolites in the process of excretion. The results show that endrin is much more rapidly metabolised in cows than in hens. The pathways of metabolism were fundamentally the same in both species, the major product being anti-12-hydroxyendrin, which was found un-conjugated in cow urine and faeces and as the O-sulphate conjugate in hen excreta. The only observed difference in primary metabolism was some syfl-12-hydroxyendrin and 12-ketoendrin in cows. This pathway was not detected in hens.