PROCEED WITH CAUTION: Protein enhancers added to pet food may have been purposefully spiked with nitrogen-based chemicals in order to make them appear to be more protein-rich. Image: © ISTOCKPHOTO/ANDREW HOWE
A month after the probe into the poisoning of pet food began, government officials announced this week that a second contaminant had been found in protein additives that have sickened or killed hundreds of dogs and cats. The announcement came on the heels of another devastating discovery: batches of rice protein concentrate used in pet food were also laced with the first known culprit, melamine, a nitrogen-based compound used in commercial and industrial plastics. The Food and Drug Administration (FDA) says the chemicals may have been deliberately added to the rice gluten in an attempt to artificially inflate the protein levels in the products.
"We have found cyanuric acid, which is somewhat related to melamine," says Stephen Sundlof, director of the FDA's Center for Veterinary Medicine. Both compounds have high levels of nitrogen, which are a measure of protein in a food product. Wheat, rice and corn glutens are forms of vegetable protein that are used as binders in soft (or wet) pet food. They can also be added to dry food to enhance the protein content, says Dave Griffin, owner of the independent pet store Westwood Pet Center in Bethesda, Md. Griffin, who has worked in the pet industry for 35 years, adds that because of lax labeling requirements, pet food manufacturers are not required to specify the source of protein—that is whether it is from meat or meal.
Brent Hoff, a clinical toxicologist and pathologist at the University of Guelph in Ontario, confirmed the presence of cyanuric acid in both the rice protein concentrate as well as in crystals found in the urine and kidneys of sick animals. Late last month, those crystals, which are brown and round in shape, were found to be made up of 30 percent melamine; the composition of the other 70 percent has yet to be determined, although it is known to contain cyanuric acid as well as amilorine and amiloride, which are by-products of melamine.
Cyanuric acid may have been added separately to the feed, however it's also likely it was present because it can result from the bacterial degradation of melamine, says Richard Goldstein, a kidney specialist at the Cornell University College of Veterinary Medicine. Much like melamine, cyanuric acid, which is typically used in chlorination during pool cleaning, is not known to have a high toxicity. "People swallow it all the time" in pool water, Goldstein says. However, he adds, "It does have a toxic effect on the kidneys in very high doses…. Combining it with melamine may cause it to crystallize and hang out in the kidneys a lot longer than normal."
Hoff and his colleagues at Guelph are continuing to analyze the crystals found in sick pets to determine "how close the crystals are to the precipitate [the solid that results when two chemicals react] of melamine and cyanuric acid." For now, though, Hoff cautions, "We haven't got it down pat."
The FDA also announced that it is taking preemptive steps to try to prevent further damage by testing protein ingredients for melamine in a variety of pet and human food, which contains protein additives—like wheat gluten and rice protein concentrate—that are imported from outside the U.S. David Acheson, chief medical officer for the agency's Center for Food Safety and Applied Nutrition, says the new measures are to determine "where else may this be" in order to keep the contaminant from sickening any more pets and, perhaps, people as well.
The number of pet food manufacturers that have yanked their products from shelves in the wake of the scandal continues to grow. Numbers of pet deaths are estimated to be in the hundreds, with one estimate counting as many as 39,000 cats and dogs as being affected by the poisoned food. The FDA for its part, however, still publicly links only 16 deaths to the contaminated products.
In addition to the pet food scare, the FDA revealed that the urine of hogs in the Carolinas and California has tested positive for melamine. The implication is that salvaged melamine-containing pet food was sold to hog producers in those states, as well as farms in New York, Utah and possibly Ohio. The FDA has quarantined all of the farms that received the tainted feed. Sundlof of the FDA says that a poultry farm in Missouri may have received contaminated food, as well. But he stressed that officials are "working to assure that there is no further distribution of the meat from these farms."