Transfer of melamine from feed to milk and from milk to cheese and whey in lactating dairy cows fed single oral doses

摘要

A study was conducted to evaluate the excretion pattern, after a single oral dose, of melamine from feed into milk, and the subsequent transfer to cheese and whey. The transfer of cyanuric acid was also investigated. Twenty-four lactating Holstein cows were randomly allocated to 4 treatments and received single doses of melamine as follows: 0.05, 0.50, 5.00, and 50.00 g/cow for groups D1, D2, D3, and D4, respectively. Individual milk samples were collected for melamine and cyanuric acid analyses on d 1, 2, 3, 4, 5, and 7. Milk collected individually from the second milking after melamine ingestion was used to make cheese on a laboratory scale. Melamine and cyanuric acid were extracted using a solid-phase extraction cartridge, and analyses were carried out by liquid chromatography-mass spectrom-etry/mass spectrometry. Maximal melamine concentrations occurred between 6 and 18 h after treatment and increased with log dose (linear and quadratic), ranging from 0.019 to 35.105 mg/kg. More than 60% of the melamine that was transferred to the milk was observed within 30 h after melamine ingestion. Melamine was not detected (limit of detection was 0.002 mg/kg) in milk 5 d after treatment in group Dl, and 7 d after treatment in groups D2, D3, and D4. Blood urea nitrogen was not influenced by melamine ingestion. During cheese making, melamine was transferred mainly to the whey fraction. Cyanuric acid was not detected in any of the samples (milk, cheese, or whey). The excretion pattern of melamine in milk and whey may represent a health concern when cows ingest more than 0.50 g of melamine/d. However, only at intake levels of 5 and 50 g/d did cheese exceed the limits as set forth by the European Union. The results confirmed that melamine contamination of milk and milk products may be related not only to direct contamination, but also to adulteration of animal feeds.