Cat Food: Mystery Ingredients Revealed

Discover how to read wet and dry cat food labels and choose the right food for your cat.

See what goes into your cat's food. Via drew_anywhere/Flickr

The endless array of pet store cat food choices astonish you. Where did all of these cat wet foods and dry foods come from? Terms such as by-products and guar gum and carrageenan locust bean are listed. What are these cat food ingredients and how can they help your cats?

With so many choices, picking the right food can be a daunting task. You can, however, look for certain things. Julie Churchill, DVM, assistant clinical specialist of companion animal nutrition at the University of Minnesota, St. Paul, suggests that when making a cat food selection, remember that all pet foods are not created nutritionally equal.

Cat Food Nutritional Claims

Cat food companies can substantiate a nutritional claim in two ways.

“First, it can claim its food was formulated to meet the Association of American Feed Control Officials [AAFCO] nutrient profiles for a particular life stage. This tells you the nutrition is in the bag, but not necessarily that it can get into the cat. A crude example of this would be to analyze a piece of shoe leather with added fat and a vitamin pill. Analytically, the nutrition is all there, but tells you nothing about important facts such as digestibility or nutrient interaction effects that may interfere with absorption,” Churchill says.

“The second way [for the cat food] is to undergo AAFCO feeding trials to establish nutritional adequacy, and this is what I recommend looking for,” Churchill says. “These foods have proven that the nutrition gets into the cat.”

The Food and Drug Administration and the U.S. Department of Agriculture regulate pet food processing. The AAFCO, an advisory committee, ensures pet food products are safe, nutritionally balanced and properly labeled. It defines cat food ingredients that can and cannot be used, nutritional standards and controls how products are named. If statements about nutrition are printed on the label, they must meet feeding protocols determined by AAFCO.

As part of the quality control process, cat food manufacturers check ingredients for adequate nutritional levels and wholesomeness before they ever go into the cat food. The food is then checked many times throughout the manufacturing process for important components such as moisture levels, fat content, protein concentration and ash.

“Manufactured pet foods are formulated, processed and packaged to protect the nutritional content over the length of time a product is on the shelf,” says Larry Hawley, manager of applied nutrition with Heinz Pet Products, Newport, Ky. Each serving must also give the required nutrition.

Consumers have the pet food industry to thank for keeping their cats healthy throughout the different stages of their lives. Through years of research, complete diets have been formulated to meet the needs of kittens, adult cats, senior cats and special needs cats.

There’s no denying most cat owners love their pets and want the very best for them. In fact, many cats probably eat a more nutritionally balanced diet than we do. Cats are eating better than ever and living longer. According to the Pet Food Institute, U.S. cat owners spent more than 4.6 million dollars on cat food in 1998, a figure that has quadrupled over the past 20 years.

Cat food is typically found in three forms: canned, dry and semimoist. While all three start with many of the same ingredients, they are processed in completely different ways.

Canned Cat Food

“Canned food is made by a process called retorting and is not much more complex than home canning,” says Daniel Carey, DVM, director of technical communications in research and development with The Iams Co., Dayton, Ohio.

The process begins with grinding meat into very small pieces and adding water to form a slurry. Dry ingredients, such as vitamins and minerals, are blended in and the mixture is pumped into the cans. Lids are applied and the cans are put into the retort, which is really a large pressure cooker. Cooking ranges from 50 to 90 minutes and temperature probes inside the can ensure the proper temperatures have been reached to kill all bacteria. Cans are then cooled and labeled.”

The complexity with retorting lies in combining time and temperature. Cook the food too long and your cat won’t want to eat it. If it is not cooked long enough, it will not be safe to eat, Carey says. Every food formula can have a different time/temperature safety combination, which is based on ingredients, how well the heat moves through the food and the size of the can.

Dry Cat Food

Dry cat food is made in a machine called an extruder, the same machine that makes breakfast cereal.

“The extruder combines a pressure cooker with a meat grinder,” Carey says. “The food goes into the extruder wet and is pushed along by a screw that lies in the center much like a meat grinder. A steam jacket that acts like a pressure cooker and cooks the food as it is moved along surrounds the machine.

“When it comes to the exit, there are two plates it is pushed through. One plate is still, and one is revolving. The moving plate slices the food as it is pushed through, and the shape of the plate determines the different shapes and sizes. A difference in pressure from inside and outside the machine causes the food to expand and puff up.”

Food can then be sprayed with tasty fat and flavor blends to make it more appealing before it is dried and packaged. Co-extrusion sends out two flavors/colors of food at the same time, one inside the other. This process forms products with filled centers.

Semimoist Cat Food

This food is manufactured using a principle called intermediate moisture technology. Semimoist cat foods stay soft because of higher levels of water; the technology keeps them from spoiling.

Water in the food is controlled by using ingredients that chemically bind it so bacteria cannot use it. Added preservatives prevent spoilage. The result is a soft and chewy product, much like canned food, that can be stored safely on the shelf. Extruders and co-extruders again form the shapes. Semimoist cat food can even be made to look as though it is layered with marbled fat.

Cat Food Taste

Commercial pet foods have tested and proven flavor appeal, Hawley says. “It’s important to feed your cat things it likes or it will just walk away from its bowl. Remember, if the cat won’t eat, it’s not getting any of the nutritional benefit. And cats’ reputation for being finicky eaters is certainly well deserved. On some occasions the same cat may like a particular food most of the time, but on a given day it suddenly may not,” Hawley says.

“We also observe that cats’ food preferences can change over time. While cats like variety, they can be very sensitive to change. When you put a new food in front of them, and they reject it, they may be responding to the fact that it is different, not to whether it is good or bad food, he says.

“There are so many factors that influence why a cat may or may not like a food,” Hawley says. “It really comes down to experimentation with your own cat. Food should not only nourish, but should provide joy to your pet. If a cat does not start to eat its food in the course of a few days, I recommend giving them another choice. But try that same food again in a month or two and don’t be surprised if the second time the cat suddenly likes it. Remember, cats are not random about their food choices and they are always subject to reversal.”

Who determines which flavor of seafood surprise is the most appealing or whether slices or shreds of beef are tastier in gravy? Some unfortunate lab technician? Luckily, no.

“At [Iams], we have a group of cats that spend their lives with us and have the daunting task of working 24 hours a day, and their job description includes eating, sleeping and using the litter box,” Carey says. “Our feline food testers try out various new food formulas and give us their opinions.”

The first test is the split preference test. “Two different bowls of food are passed underneath the cat’s nose and then placed down for them to eat from. We watch to see which bowl the cat eats out of first. This first choice indicates a preference for aroma and possibly appearance. We measure how much the cat has eaten from both bowls during a mealtime of 30 minutes. The amount of food eaten may be different from the first bite preference. While the cat may like the smell of one food, after a few bites it may decide although it smells great, it has a funny taste or texture and they move on to the other food.”

The second test is the acceptability test. “This measures whether or not a cat will eat enough of a certain food to maintain its body weight,” Carey says. “They may really like the food, but may eat only half of the total calories needed. A final test actually tests the cat tasting ability. We put them through a series of tests to make sure that they are discriminating from two different bowls of food.”

Cat food formulas go through months and months of development, testing and re-formation before they ever reach store shelves. Developing the ingredients is only the half of it. The next task is to find out what form the cats prefer to eat.

“People do not understand the legal definition of these ingredients or their benefit to the animal,” she says. “You have to consider the natural instincts of the cat. Cats eat whole mice, not just the skeletal muscle. The mouse diet is probably the ideal optimal nutritional level for a cat. Many pet food companies have studied the nutritional content in the mouse diet and base their nutritional knowledge on it.”

Matching the nutritional content of the whole mouse is often best achieved through the use of meat by-products.

Choosing a Cat Food

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