• Canned food is essential for cats.  As an animal that evolved in the desert where water is scarce, a cat’s system naturally concentrates their urine, and is designed to obtain moisture mainly from food (a mouse is about 75% fluids). Dry food must absorb moisture in order to be digested, which dehydrates the system and leads to even further concentration of the urine, promoting feline lower urinary tract disease. Eating canned food provides the fluids necessary for internal organs to function properly, which can help to prevent serious health problems, such as diabetes, urinary blockages, chronic constipation, and kidney failure. Free feeding dry food, which is high in carbohydrates and starch, is one of the leading causes of obesity in felines. Dry food can also promote tooth decay, and should not be included in a cat’s diet.
  • Look for protein. Cats are obligate carnivores, meaning that their digestive system is designed to primarily accommodate meat and other proteins. Therefore, the primary (first three) ingredients in the food that they eat should include poultry, beef or fish. Some cats do best on a properly balanced raw diet, and there are a number of raw diets especially prepared for cats available in the freezer section at pet stores. Do not feed your cat raw meat from the grocery store and assume that it will be a balanced diet, as this will result in serious health problems due to lack of essential vitamins.
  • Feed fish sparingly. Seafood sensitivities and allergies are very common in cats, especially with salmon. This is thought to be due to the large amount of histamines that are in caught fish. Signs of allergies are itching and other skin problems, whereas a sensitivity will result in diarrhea or vomiting. The primary fish used in cat food are salmon, tuna, and tilefish (a.k.a. ocean whitefish). Most salmon are farm-raised with antifungals and antibiotics, and are often laced with ocean pollutants such as PCBs and pesticides. Tuna accumulate high levels of mercury and other heavy metals in addition to these ocean pollutants and toxins by eating smaller fish. Tilefish are so heavily contaminated that the FDA advises women of child-bearing age and children to avoid them entirely. Fish should be rotated with poultry rather than fed exclusively.
  • Avoid foods with artificial colors, flavors, and preservatives. Some cats have allergies to dyes and preservatives, and they can also be hard on your cat’s internal organs.
  • Read the labels! Given the absence of rigorous comparison testing, a food’s nutritional data is the best guide to quality. If cost, availability, or your cat’s preferences are an issue, find foods high in protein and low in carbohydrates that are in your price range that your cat likes.
  • Pet food safety remains a concern. Past recalls of cat foods because of tainted wheat and rice glutens have spotlighted some major issues regarding pet foods and their ingredients. It is a good idea to keep a watchful eye on pet foods for the foreseeable future. The FDA and ASPCA websites are excellent resources.
  • Re-evaluate food labels periodically. Cat food formulas can change, and pet food manufacturers aren’t required to change the name of the product or otherwise declare that the formula has been altered.
  • Websites for research: 

https://feline-nutrition.org/health/species-inappropriate-the-dangers-of-dry-food

http://www.blakkatz.com/dryfood.html

http://www.catinfo.org/

http://www.askavetquestion.com/nutrition/chicken-byproducts/