Abstract
The objectives of this paper were to evaluate the effects of feeding diets containing different levels of melamine on melamine concentrations in milk, plasma, rumen fluid, urine and feces in Holstein dairy cows. Sixteen Chinese Holstein dairy cows fixed with permanent ruminal cannulas were assigned to 1 of 4 treatments within a completely randomized design for 10 days. Cows were fed different amounts of melamine {20 (group 1), 40 (group 2), 60 (group 3) or 80 (group 4) g/day/cow} once daily in the morning mixed with a melamine free basal diet for 7-days adaptation followed by 3-days urine and feces sample collections. Melamine was found in all samples tested and its concentration generally increased as dose increased in the diet. These results indicated that different doses of melamine in the diet could result in different concentrations of melamine in milk, plasma, rumen fluid, urine and feces. Data suggested that melamine primarily cleared by urinary excretion, followed by fecal excretion in lactating dairy cows. Mammary tissue was apparently not a major tissue to dispose melamine, especially when fed a relatively low dose (lower than 40 g/day/cow). Key words: Melamine, excretion, lactating dairy cow.
Highlights
The fact that melamine appeared in pet food and milk products (World Health Organization, 2008) have induced a widespread food safety consideration
These results indicated that different doses of melamine in the diet could result in different concentrations of melamine in milk, plasma, rumen fluid, urine and feces
A driving force for the adulteration of feedstuff and milk products with melamine is that its high nitrogen content (66% nitrogen by mass) increases the apparent protein content detected by standard protein analysis tests, for instance, Kjeldahl or Dumas, which consider the total nitrogen level as the indicator of the protein content
Summary
The fact that melamine appeared in pet food and milk products (World Health Organization, 2008) have induced a widespread food safety consideration. A driving force for the adulteration of feedstuff and milk products with melamine is that its high nitrogen content (66% nitrogen by mass) increases the apparent protein content detected by standard protein analysis tests, for instance, Kjeldahl or Dumas, which consider the total nitrogen level as the indicator of the protein content. The FDA’s safety/risk assessment (2007) concluded that a 63 mg of melamine/kg dose in diet is safe. The contaminated pet food was incorporated into the food supply of several different food animal species. Melamine contamination was determined to a level of 30 to 120 ppm in swine feed (US-FDA, 2007). The public is concerned about consuming milk from cows exposed to melamine.
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