Toxicity of dietary melamine to laying ducks: biochemical and histopathological changes and residue in eggs

Jinding laying ducks (n = 648) were subjected to one of six dietary treatments (0, 1, 5, 25, 50, or 100 mg of melamine/kg of diet) to investigate the toxicity of melamine and determine the melamine residue in eggs. Ducks were fed melamine-supplemented diets for 21 days followed by a 21 day withdrawal period. Dietary melamine had no adverse effects on laying performance. Renal lesions were correlated with increasing levels of dietary melamine. Melamine residue in eggs increased with dietary melamine during the first 21 days and reached the maximum content (1.35 mg/kg) in the 100 mg of melamine/kg of diet group. Melamine residue in eggs decreased rapidly during the withdrawal period. The depletion time for egg melamine residue increased with dietary melamine level. These results indicated that a dietary level of > or = 50 mg of melamine/kg of feed induces obvious renal injury. The residue level and withdrawal time for melamine clearance in eggs correlated with the dietary melamine level.