A second industrial chemical that regulators have found in contaminated pet food in the United States may have also been intentionally added to animal feed by producers seeking larger profits, according to interviews with chemical industry officials here.
Three Chinese chemical makers said that producers of animal feed often purchase or seek to purchase a chemical called cyanuric acid from their factories to blend into animal feed.
Chemical producers said that it was common knowledge that for years cyanuric acid was used in animal and fish feed in China. In the United States, cyanuric acid is often used as a disinfectant in swimming pools.
Two of the chemical makers said feed producers here used it because it was high in nitrogen, enabling feed producers to artificially increase the protein reading of the feed.
"Cyanuric acid scrap can be added to animal feed," said Yu Luwei, general manager of Juancheng Ouya Chemical Company in Shandong Province. "I sell it to fish meal manufacturers and fish farmers. It an also be added to feed for other animals."
The revelation is interesting not just because it is another indication that Chinese animal feed producers were intentionally doctoring the ingredients they sold but because the practice of using cyanuric acid may provide clues as to why the pet food in the United States became so poisonous.
American regulators already suspect that Chinese companies mixed an industrial chemical called melamine into animal feed because it is high in nitrogen and can be used to artificially bolster protein levels.
In recent weeks, scientists trying to determine what led to one of the largest pet food recalls in history say the deaths and illness of thousands of pets in the United States have been linked to melamine and other melamine-related compounds.
But scientists have had difficulty finding the precise cause of the deaths. Neither melamine nor cyanuric acid, which is a melamine-like compound, is thought to be particularly toxic.
Now, however, scientists studying the pet food deaths say the combination of the two chemicals, mixed together with perhaps some other related compounds, may have created a toxic punch that formed crystals in the kidneys of pets and led to kidney failure.
"I'm convinced melamine can't do it by itself," said Richard Goldstein, an assistant professor at the Cornell University College of Veterinary Medicine. "I think it's this melamine with other compounds that is toxic."
Scientists and veterinarians in the United States and South Africa say that contaminated batches of wheat gluten, corn protein and rice protein sold to pet food makers often contained a mixture of melamine and cyanuric acid.
In South Africa, about 30 dogs died earlier this year from pet food imported from China that was tainted with melamine and cyanuric acid.
Fred Reyers, a veterinary clinical pathologist in South Africa, said that he thinks that either impure melamine or impure cyanuric acid mixed together formed crystals in pets that blocked the kidneys and led to kidney failure.
"This may be an unexpected byproduct in manufacturing melamine," he said. "When you make melamine, on the edges, you get impurities."
Recently in the United States, some contaminated pet food and protein meal also found its way into hog and chicken feed, which led the government to ask farms to quarantine and slaughter some animals as a precautionary measure.
But on Monday, a joint assessment by scientists working for the Food and Drug Administration, the United States Department of Agriculture and several other federal agencies said there was a very low risk of danger to humans who consume meat from animals that were accidentally fed melamine-tainted feed.
The scientists said the dilution was a major factor in lowering the risk. The government also said that both chickens and hogs fed the melamine-tainted feed appear to be healthy.
But in pets, which apparently consumed a higher concentration of melamine, the result was often kidney failure or death.
F.D.A. officials were in China last week and may still be here meeting government officials and trying to visit factories to better determine why melamine was placed in the feed.
But interviews with Chinese animal feed producers, melamine companies and traders and other chemical makers over the last two weeks indicate that melamine and cyanuric acid are often added intentionally to animal feed to cheat buyers.
"I've heard that people add cyanuric acid and melamine to animal feed to boost the protein level," said Yang Fei, who works in the sales department of the Shouguang Weidong Chemical Company, which is in Shandong Province, where some of the contaminated pet food ingredients came from.
Shao Gen, general manager at another chemical maker, the Tengzhou Yinfeng Chemical Company, said cyanuric acid can be added to fish feed, noting it's not nutritious but can help clean up the fish pond.
He added: "It can probably be added to feed for other animals. Is it legal? There is no law banning the practice. As far as I know, the practice was imported from other countries."
Animal feed producers say they can buy a lower grade of protein, and then mix in a little melamine, which is high in nitrogen. The meal then appears to have higher protein because protein readings are usually noted by reading nitrogen levels.
Often, the animal feed producers say they do not buy pure melamine, which is used to make plastics and fertilizer, but impure melamine scrap from chemical factories, which is much cheaper than pure melamine.
Feed producers say they believed it to be legal and nontoxic, though they acknowledge they are cheating buyers. Scientists looking at the pet food deaths, however, say melamine scrap may have impurities and related compounds, like cyanuric acid, which could turn it more toxic.
Chinese chemical makers say they also produce a chemical which is a combination of melamine and cyanuric acid, and that feed producers have often sought to purchase scrap material from this product.
Melamine scrap or cyanuric acid scrap often costs one quarter of the price of pure melamine or cyanuric acid and is much cheaper per protein count than wheat or corn meal.
Cyanuric acid scrap is often even cheaper than melamine scrap, producers here say, which is one reason it may have been mixed in or used as a substitute for melamine in the pet food ingredients.
Many producers here say they aren't aware of the regulations forbidding the use of melamine or cyanuric acid in animal feed and they say they do not know it is potentially harmful.
"The substance is nontoxic; it's legal to add it to animal feed," Mr. Yu at Juancheng Ouya Chemical, said of the sale of cyanuric acid. "The practice has been around for many years. I often sell it to animal feed makers."
- 182 Health