Today we are going to discuss various pet food manufacturing processes, various recall issues and the potential dangers with pet food laying ahead of us to continue this series contributed by Born Free USA united with Animal Protection Institute. In Part 1 of this series we briefly introduced the subject matter and discussed the major players in the pet food industry. But as we have learned the trend to bigger doesn’t necessarily translate into better and unfortunately we learned, not that it would be anything new, that there are major differences between what pet owners think they are buying and what they are actually getting. Part 2 addressed in very general terms labeling basics, standards and regulations, while Part 3 focused on ingredients. This series focuses in very general terms on the most visible name brands, the pet food labels that are mass-distributed to supermarkets and discount stores. However, just so that we are on the safe side, there are also many highly respected brands that may be guilty of the same offenses. What many pet owners to this day still don’t know is that the pet food industry is an extension of the human food and agriculture industries. Pet food provides a convenient way for slaughterhouse offal, grains considered “unfit for human consumption,” and similar waste products to be turned into profit. In order for the consumer to make an educated decision it is necessary to learn, among many others considerations, how to read pet food labels to begin with.
The Manufacturing Process: How Pet Food Is Made
The vast majority of dry food is made with a machine called an extruder. First, materials are blended in accordance with a recipe created with the help of computer programs that provide the nutrient content of each proposed ingredient. For instance, corn gluten meal has more protein than wheat flour. Because the extruder needs a consistent amount of starch and low moisture to work properly, dry ingredients — such as rendered meat-and-bone-meal, poultry by-product meal, grains, and flours — predominate.
The dough is fed into the screws of an extruder. It is subjected to steam and high pressure as it is pushed through dies that determine the shape of the final product, much like the nozzles used in cake decorating. As the hot, pressurized dough exits the extruder, it is cut by a set of rapidly whirling knives into tiny pieces. As the dough reaches normal air pressure, it expands or “puffs” into its final shape. The food is allowed to dry, and then is usually sprayed with fat, digests, or other compounds to make it more palatable. When it is cooled, it can be bagged.
Although the cooking process kills bacteria in the ingredients, the final product can pick up more bacteria during the subsequent drying, coating, and packaging process. Some experts warn that getting dry food wet can allow the bacteria on the surface to multiply and make pets sick. Do not mix dry food with water, milk, canned food, or other liquids.
A few dog foods are baked at high temperatures (over 500°F) rather than extruded. This produces a sheet of dense, crunchy material that is then broken into irregular chunks, much like crumbling crackers into soup. It is relatively palatable without the sprayed-on fats and other enhancers needed on extruded dry food.
Semi-moist foods and many pet treats are also made with an extruder. To be appealing to consumers and to keep their texture, they contain many additives, colorings, and preservatives; they are not a good choice for a pet’s primary diet.
Wet or canned food begins with ground ingredients mixed with additives. If chunks are required, a special extruder forms them. Then the mixture is cooked and canned. The sealed cans are then put into containers resembling pressure cookers and commercial sterilization takes place. Some manufacturers cook the food right in the can.
Wet foods are quite different in content from dry or semi-moist foods. While many canned foods contain by-products of various sorts, they are “fresh” and not rendered or processed (although they are often frozen for transport and storage). Wet foods usually contain much more protein, and it’s often a little higher quality, than dry foods. They also have more moisture, which is better for cats. They are packaged in cans or pouches.
Comparing Food Types
Because of the variation in water content, it is impossible to directly compare labels from different kinds of food without a mathematical conversion to “dry matter basis.” The numbers can be very deceiving. For instance, a canned food containing 10% protein actually has much more protein than a dry food with 30% protein.
To put the foods on a level playing field, first calculate the dry matter content by subtracting the moisture content given on the label from 100%. Then divide the ingredient by the dry matter content. For example, a typical bag of dry cat food contains 30% protein on the label, but 32% on a dry-matter basis (30% divided by its dry matter content, 100-6% moisture = 94%). A can of cat food might contain 12% protein on the label, but almost 43% on a dry-matter basis (12% divided by its dry matter content, 100-72% moisture = 28%). Dry food typically contains less than 10% water, while canned food contains 78% or more water.
Given the types of things manufacturers put in pet food, it is not surprising that bad things sometimes happen. Ingredients used in pet food are often highly contaminated with a wide variety of toxic substances. Some of these are destroyed by processing, but others are not.
Bacteria. Slaughtered animals, as well as those that have died because of disease, injury, or natural causes, are sources of meat, by-products, and rendered meals. An animal that died on the farm might not reach a rendering plant until days after its death. Therefore the carcass is often contaminated with bacteria such as Salmonella and E. coli. Dangerous E. Coli bacteria are estimated to contaminate more than 50% of meat meals. While the cooking process may kill bacteria, it does not eliminate the endotoxins some bacteria produce during their growth. These toxins can survive processing, and can cause sickness and disease. Pet food manufacturers do not test their products for bacterial endotoxins. Because sick or dead animals can be processed as pet foods, the drugs that were used to treat or euthanize them may still be present in the end product. Penicillin and pentobarbital are just two examples of drugs that can pass through processing unchanged. Antibiotics used in livestock production are also thought to contribute to antibiotic resistance in humans.
Mycotoxins. Toxins from mold or fungi are called mycotoxins. Modern farming practices, adverse weather conditions, and improper drying and storage of crops can contribute to mold growth. Pet food ingredients that are most likely to be contaminated with mycotoxins are grains such as wheat and corn, and fish meal.
Chemical Residue. Pesticides and fertilizers may leave residue on plant products. Grains that are condemned for human consumption by the USDA due to residue may legally be used, without limitation, in pet food.
GMOs. Genetically modified plant products are also of concern. By 2006, 89% of the planted area of soybeans, 83% of cotton, and 61% of maize (corn) in the U.S. were genetically modified varieties. Cottonseed meal is a common ingredient of cattle feed; soy and corn are used directly in many pet foods.
Acrylamide. This is a carcinogenic compound formed at cooking temperatures of about 250°F in foods containing certain sugars and the amino acid asparagine (found in large amounts in potatoes and cereal grains). It is formed in a chemical process called the Maillard reaction.4, 5 Most dry pet foods contain cereal grains or potatoes, and they are processed at high temperatures (200–300°F at high pressure during extrusion; baked foods are cooked at well over 500°F); these are perfect conditions for the Maillard reaction. In fact, the Maillard reaction is considered desirable in the production of pet food because it imparts a palatable taste, even though it reduces the bioavailability of some amino acids, including taurine and lysine.6 The content and potential effects of acrylamide formation in pet foods are unknown.
Pet Food Recalls
When things go really wrong and serious problems are discovered in pet food, the company usually works with the FDA to coordinate a recall of the affected products. While many recalls have been widely publicized, quite a few have not.
In 1995, Nature’s Recipe recalled almost a million pounds of dry dog and cat food after consumers complained that their pets were vomiting and losing their appetite. The problem was a fungus that produced vomitoxin contaminating the wheat.
In 1999, Doane Pet Care recalled more than a million bags of corn-based dry dog food contaminated with aflatoxin. Products included Ol’ Roy (Wal-Mart’s brand) and 53 other brands. This time, the toxin killed 25 dogs.
In 2000, Iams recalled 248,000 pounds of dry dog food distributed in 7 states due to excess DL-Methionine Amino Acid, a urinary acidifier.
In 2003, a recall was made by Petcurean “Go! Natural” pet food due to circumstantial association with some dogs suffering from liver disease; no cause was ever found.
In late 2005, a similar recall by Diamond Foods was announced; this time the moldy corn contained a particularly nasty fungal product called aflatoxin; 100 dogs died.
Also in 2005, 123,000 pounds of cat and dog treats were recalled due to Salmonella contamination.
In 2006, more than 5 million cans of Ol’ Roy, American Fare, and other dog foods distributed in the southeast were recalled by the manufacturer, Simmons Pet Food, because the cans’ enamel lining was flaking off into the food.
Also in 2006, Merrick Pet Care recalled almost 200,000 cans of “Wingalings” dog food when metal tags were found in some samples.
In the most deadly recall of 2006, 4 prescription canned dog and cat foods were recalled by Royal Canin (owned by Mars). The culprit was a serious overdose of Vitamin D that caused calcium deficiency and kidney disease.
In February 2007, the FDA issued a warning to consumers not to buy “Wild Kitty,” a frozen food containing raw meat. Routine testing by FDA had revealed Salmonella in the food. FDA specifically warned about the potential for illness in humans, not pets. There were no reports of illness or death of any pets, and the food was not recalled.
In March 2007, the most lethal pet food in history was the subject of the largest recall ever. Menu Foods recalled more than 100 brands including Iams, Eukanuba, Hill’s Science Diet, Purina Mighty Dog, and many store brands including Wal-Mart’s. Thousands of pets were sickened (the FDA received more than 17,000 reports) and an estimated 20% died from acute renal failure caused by the food. Cats were more frequently and more severely affected than dogs. The toxin was initially believed to be a pesticide, the rat poison “aminopterin” in one of the ingredients. In April, scientists discovered high levels of melamine, a chemical used in plastics and fertilizers, in wheat gluten and rice protein concentrate imported from China. The melamine had been purposefully added to the ingredients to falsely boost their protein content. Subsequent tests revealed that the melamine-tainted ingredients had also been used in feed for cows, pigs, and chickens and thousands of animals were quarantined and destroyed. In early May, scientists identified the cause of the rapid onset kidney disease that had appeared in dogs and cats as a reaction caused by the combination of melamine and cyanuric acid, both unauthorized chemicals.
Stay tuned for the discussion about nutrition related diseases in part 5 soon to follow.
Reprinted with permission from and contributed by Born Free USA united with Animal Protection Institute and reprinted with permission. © 2003-2009 - Born Free USA united with Animal Protection Institute - All rights reserved