Disposition of melamine residues in blood and milk from dairy goats exposed to an oral bolus of melamine

There have been numerous reports of melamine-related illnesses following oral exposure to this contaminant. These studies have been in monogastrics, but there are few reports of adverse effects and pharmacokinetics of melamine in ruminants. The purpose of this project was to determine how melamine is systemically cleared from the blood and milk in lactating animals. Five lactating goats were given a single oral dose of 40 mg/kg body weight. Milk and blood samples were collected for 144 h and analyzed to determine key pharmacokinetic parameters. The apparent plasma half-life (11.12 h) was 3 times longer in these ruminants than that reported in monogastrics and the apparent volume of distribution was more than 6 times greater than that reported in monogastrics. The milk had an apparent half-life of 9.44 h and less than 0.4% of the melamine dose was eliminated in milk. All milk samples were below the LOQ at 4 days (96 h) after exposure. In summary, the pharmacokinetics of melamine in ruminants is not predictive from monogastrics and milk from similarly exposed animals should be condemned for at least 4 days after the last exposure to avoid violation of proposed MRLs or safe levels for milk.