The Classic Comprehensive Handbook of Cat Care
CHOOSING A CAT FOOD
Commercial rations for cats are sold as dry foods, semimoist (soft- moist) foods, and canned foods. Each type of product can provide complete nutrition for your pet if it is formulated correctly.
In general it is most economical to use dry food (about 10% moisture content) as a cat’s basic diet. Its low moisture content allows it to be left out for a cat to consume at will without its spoiling in all but the most humid climates. Its crunchy texture helps keep a cat’s teeth clean, which is very important since many cats are subject to dental disease. However, dry foods, even well balanced, cannot mimic the foods a cat would eat naturally. They contain much larger amounts of vegetable material than a cat would naturally consume, and some products contain artificial flavors, coloring agents, and preservatives to which some cats are intolerant. Cats also consume less total water (around 50% less) when eating dry foods compared to canned food although they drink more. This can become a health issue for older cats with kidney disease and/or constipation, or for cats who have urinary tract disease. Dry foods may become deficient in essential fatty acids when stored, especially when the weather is warm and humid. Their physical composition allows less fat to be incorporated initially, and contact with the oxygen in the air makes the fat present turn rancid. Do not store dry foods at room temperature for longer than six months; purchase them from dealers who have a rapid food turnover. Although many dry products provide excellent complete nutrition and many cats do well eating dry foods alone, the most healthful diet for a cat should include some other foods as well.
Semimoist cat foods are intermediate in moisture content (about 25% to 35%) and are usually designed to be nutritionally complete. Semimoist foods are considerably more expensive than dry foods if the additional water they contain is taken into consideration when calculating the cost per feeding. Chemical humectants (e.g., propylene glycol), corn syrup, salts, sugar, and acids are used to hold water in these products and keep them soft and free from spoilage. Also semimoist products often contain artificial flavors and colors. They are generally quite palatable to cats and convenient for their owners, since such foods can be stored for months at room temperature if unopened and they are often sold in single-feeding pouches.
Unfortunately, semimoist foods give none of the tooth-cleaning benefit of dry foods, and they cannot begin to approach the more natural quality of the best canned foods. Propylene glycol, a common preservative and energy source used in semimoist food for years causes oxidative damage to cats’ red blood cells and will be required by law to be eliminated from cat foods sold in the United States by the end of 1993. Reserve semimoist foods for snacks.
Canned products tend to be the most expensive way to feed cats since you pay for about 75% water. They are, however, safe to store for prolonged periods and highly palatable to cats. Their formulation allows the best manufacturers to include ingredients such as meat and liver and high levels of fat that mimic the components of a diet a cat might naturally prey upon. Complete canned foods are a desirable part of a cat’s diet, but you must be careful to read package labels (see chart) to be sure your cat is getting products intended to be fed as complete diets. Incomplete “gourmet” products should be fed only as dietary supplements. If the label does not make it clear that the food is intended to be complete in itself, use the product only in addition to a wide variety of other foods.
Heat processing destroys important vitamins (e.g., thiamine) and other nutrients (e.g., taurine), so all complete canned products will show evidence of supplementation in the list of ingredients on their labels. Some canned products contain artificial flavors, colors, and preservatives such as sodium nitrite. Like propylene glycol, sodium nitrite has been shown to induce oxidative damage to cats’ red blood cells. To feed the most natural diet to your cat, avoid canned products that contain such additives.
Federal law requires that all cat foods in interstate commerce carry a listing of ingredients in decreasing order of predominance. Other regulations require a guaranteed analysis, listing minimum or maximum levels of certain nutrients present on an as-fed basis (i.e., not corrected for the amount of moisture present). Unfortunately, the required labels do not contain enough information to enable you to compare cat foods adequately with one another. The guaranteed analysis gives no indication of the quality of the nutrients present, nor does it give the exact quantities present. Companies are restricted from misrepresenting their products, however, and certain large manufacturers of cat foods have conducted extensive research and feeding trials in order to produce nutritious diets that need no supplementation. These foods carry labels that indicate their nutritional adequacy based on calculation, chemical analysis, or feeding trials (the best).
The following rules of thumb will help you choose a cat food:
- Look at the food. This is a fairly effective way of evaluating many canned foods. If you see pieces of bone, discolored meat, and poorly digestible items such as blood vessels and skin, it’s a pretty good indication of poor quality food.
- Consider the price. Cheap cat foods often contain cheap ingredients —poor quality protein and poorly digestible nutrients that pass through your cat unused. “Gourmet”-type cat foods, on the other hand, may contain high- quality ingredients but are often relatively overpriced.
- Well-known manufacturers noted for their research generally produce good-quality cat foods you can trust.
- See what kind of effect the food has when eaten. If your cat gets diarrhea or becomes flatulent on a food, it’s not the diet you should continue to feed. Voluminous stools following feeding of certain brands of food often indicate excessive amounts of fiber or other indigestible substances. Good products are 75% to 80% absorbed by the gut unless specifically formulated to be therapeutic high-fiber foods.
- Read the label and choose only products that have label claims of complete nutrition. Those that indicate they are adequate for all life stages based on feeding trials are the products that have stood up to the most rigorous testing. Calculation or chemical analysis cannot measure exactly how the product will be utilized by the cat.
- Calculate the cost per feeding, since the price per bag, can, or box may be misleading. Record the cost per package and the purchase date. When empty, divide the price by the number of days it took to finish the product. The most “expensive” foods per package are often less expensive to feed per day than the apparently cheaper brands, as less volume is needed to provide proper nutrition.
- Write or call the food manufacturer to obtain any additional information you might need. For example, the protein and dry-matter digestibility of good foods usually exceeds 80%. This information, however, is often not available on the food label. Reputable food manufacturers are happy to provide the customer with information and often provide toll-free numbers for this purpose.
PET FOOD LABELS
Pet food labels are legal documents that must include the following information unless they are intended to be used solely as treats or snacks and are labeled as such:
- Name of product
- Animal species for which it is to be used
- Net weight of the product
- Ingredient list in descending order of content of the ingredients
- Guaranteed analysis listing protein, fat (minimum), and fiber and moisture (maximum) content
- Manufacturer’s name and address
- Nutritional adequacy claim An example: Complete (contains adequate levels of all required nutrients) and balanced (contains the proper proportions of required nutrients) for all life stages (will support kitten growth, pregnancy, and nursing, in addition to maintaining the adult cat).
Nutritionally incomplete products not labeled as snacks or treats must carry a statement that the “product is intended for intermittent or supplemental feeding only.” To understand lists of ingredients fully, consult another reference, since pet food manufacturers use a language of their own. For example: A beef-flavored product does not have to contain any actual beef muscle meat. The best reference is the Manual of the Association of American Feed Control Officials (AAFCO), which is published annually.
To compare foods adequately to one another, differences due to water content must be eliminated. To do this, first calculate the percentage of dry matter: 100% – moisture = percentage total dry matter To calculate the amount of nutrient present on a dry basis (e.g., percent protein on a dry-matter basis): guaranteed percent of nutrient as fed/percent dry matter X 100 = percent nutrient present on dry basis