There are so many choices available for pet foods these days, it can be overwhelming. Armed with a little knowledge and common sense, you can choose a healthy, balanced and safe diet for your pet.
Firstly, it's important to know there are a lot of marketing myths that can add to the confusion. Are grains inherently bad for dogs and cats? Absolutely not and they can provide a healthy source of protein and fiber if provided in the right balance with other nutrients. Domesticated dogs and cats have evolved significantly from their ancestors, but even their ancestors had some grains in their diets. Wild cats and dogs consume grains within their preys' gastrointestinal tracts, as well as "graze" on some grasses and grains. So grains can be a part of a healthy, balanced diet for dogs and cats, though it's not recommended that they constitute the main source of protein.
Cats are obligate carnivores and require a high percentage of protein and limited carbohydrates in the diet. In particular, it's best to limit carbohydrates in most cats to between 2-12% of their caloric intake. Domestic dogs are more tolerant of carbohydrates and have actually evolved over the last 10,000 years to digest starches and carbohydrates better than their wolf relatives. It's not unusual to see dogs thriving on diets with over 50% carbohydrate content.
When choosing a protein source, it's tempting to go for the exotic: Bison! Wild boar! Tilapia! But if we think about what cats would naturally eat -- small critters such as birds, bunnies and mice -- then poultry and rabbit make more sense. Also, cats don't naturally catch and eat fish for the most part. In fact, large animal proteins such as beef and lamb, as well as fish and seafood, are among the biggest offenders in adverse food reactions in cats. Dogs are also more likely to react to beef than other proteins.