Tissue deposition and residue depletion in laying hens exposed to melamine-contaminated diets.

To investigate the deposition and elimination of melamine in hen eggs and tissues, 72 Roman laying hens were administrated with melamine at 8.6-140.9 mg per kilogram of body weight per day for 34 days. The crystals were found in one of three kidneys of hens treated with melamine at either 62.6 or 140.9 mg/kg. Furthermore, the melamine concentrations in egg, muscle, liver, kidney, stomach, duodenum, uterus, ovary, and blood plasma were determined by high-performance liquid chromatography-ultraviolet (HPLC-UV) methods. A higher dosage of melamine in the diet corresponded to higher concentrations in tissues and eggs. The concentrations of melamine in tissues were in the following ranges (microg/g): egg, 1.1-28.7; muscle, 0.4-9.3; liver, 0.5-6.9; kidney, 1.3-21.7; stomach, 0.4-7.3; duodenum, 0.3-2.8; uterus, 0.5-6.9; ovary, 0.5-9.1; and blood plasma, 0.8-7.6. When melamine was withdrawn from the diet of hens, the melamine concentration in hen tissues fell to below 2.5 microg/g by day 10 and no residues were detected in eggs or tissues at days 7 and 20, respectively.