Backgrounder on Melamine

Pet food used in animal feeding operations

April 2007

Pork producers and feed use

Pork producers feed their hogs a nutritionally-balanced, corn and soybean-based diet. In certain regions, where alternative ingredients such as bread and bakery waste, biofuel production byproducts or surplus pet food are available, these are sometimes included, in accordance with USDA regulations, as feed ingredients.

On April 3 and April 14, Diamond Pet Foods, a pet food manufacturer in Lathrop, Calif., delivered pet food to a hog farm (American Hog Farm) in Ceres, Calif. The pet food is believed to have been included in a pet food recall initiated on April 16.

On April 19, the California Department of Food and Agriculture, quarantined the California farm and laboratory testing revealed the presence of melamine in pig urine. Additional testing of tissues, serum and urine from animals at the farm is under way at the California Animal Health and Food Safety Laboratory at University of California-Davis.

At this time, the risk to human health has been deemed minimal by the California Department of Food and Agriculture and the FDA, but has yet to be confirmed.

Hog farms in California, North Carolina, South Carolina, Utah, New York and possibly Ohio may have received tainted pet food. The investigation by the FDA is ongoing.

As of April 24, authorities have confirmed that only farms in California, North Carolina and South Carolina have received the tainted pet food. State authorities have taken the appropriate action, facilities have been quarantined to prevent any movement of animals and the producers are working with Animal and Plant Health Inspection Service (APHIS) and Food Safety and Inspection Service (FSIS) to prevent the distribution of pork originating for these farms until the risk to human health is determined.

A poultry farm in Missouri may have received tainted pet food as well.

Pet food recall

The pet food recall has affected mostly moist pet food (also known as “cuts and gravy”), but also some dry pet food (“kibble”).

Various toxic substances have been linked to the recall. Initially, aminopterin, a cancer drug also used as rat poison was considered the likely culprit. The U.S. Food and Drug Administration (FDA) has said it cannot confirm that finding. Since then, melamine and melamine-related products in wheat gluten and rice protein concentrate have also been suspected as contaminants. The FDA is not 100 percent certain that melamine is the cause of the pet illnesses and deaths. Although some studies have shown a toxic effect of melamine in rodents, research is scarce on melamine’s effect on cats and dogs.

A voluntary pet food recall for pet food products containing wheat gluten started on March 16; a voluntary recall for products containing rice protein concentrate started on April 16.

Updated information on the pet food recall can be found online at

At this time, the pet food recall affecting hog farms appears to be only of dry food containing contaminated rice protein concentrate.

Food safety

As of today, the risk to human health from consuming meat from hogs that may have consumed melamine tainted pet food has been deemed minimal by the California Department of Food and Agriculture and the FDA, but has yet to be confirmed.

The affected farms have been quarantined and authorities are working to determine the risk to humans from consuming pork from operations that may have used adulterated pet food.


Wheat gluten is a mixture of two proteins obtained when wheat flour is washed to remove the starch. It is sometimes used to thicken pet food “gravy.” It also brings elasticity and texture to baked or dry products.

Rice protein concentrate, also known as rice gluten, is the byproduct of producing rice starch in wet milling. It is considered a filler and an inexpensive source of protein in pet food manufacturing.

Melamine has a number of industrial uses. It is used in manufacturing plastics in the United States (some uses for melamine include cooking utensils and countertops); and fertilizers in Asia. In the United States it has no approved use in human or animal food, nor is it permitted to be used as fertilizer.

Melamine has been found in wheat gluten, rice protein concentrate imported into this country from China. The substance has also been found in corn gluten shipped from China to South Africa.

On April 24, authorities announced they are taking a proactive step and have begun testing for melamine and melamine-related contaminants in imported corn gluten, rice bran, corn meal, soy protein in addition to rice protein concentrate and wheat gluten.

In the United States, food safety is regulated by the FDA and FSIS. ( and

Date published: 2007-04-03