Pet food is plant or animal material intended for consumption by pets. Typically sold in pet stores and supermarkets, it is usually specific to the type of animal, such as dog food or cat food. Most meat used for non-human animals is a by-product of the human food industry, and is not regarded as "human grade.
Fish foods normally contain macro nutrients, trace elements and vitamins necessary to keep captive fish in good health. Approximately 80% of fishkeeping hobbyists feed their fish exclusively prepared foods that most commonly are produced in flake, pellet or tablet form. Pelleted forms, some of which sink rapidly, are often used for larger fish or bottom feeding species such as loaches or catfish. Some fish foods also contain additives, such as beta carotene or sex hormones, to artificially enhance the color of ornamental fish.
Bird food are used both in birdfeeders and to feed pet birds. It typically consist of a variety of seeds. Not all birds eat seeds. Suet (beef or mutton fat) is recommended for insect-eating birds like nuthatches and woodpeckers. Nectar (essentially sugar water) attracts hummingbirds.
Cats are obligate carnivores, though most commercial cat food contains both animal and plant material supplemented with vitamins, minerals and other nutrients. Cat food is formulated to address the specific nutritional requirements of cats, in particular containing the amino acid taurine, as cats cannot thrive on taurine-deficient food.
There are many different recommendations on what diet is best for dogs. Some people argue that dogs have thrived off of leftovers and scraps from their human owners for thousands of years and that commercial dog foods (which have only been available for the past century) contain poor-quality meats, additives, and other ingredients dogs should not ingest, or that commercial dog food is not nutritionally sufficient for their dogs. Most store-bought pet food comes in either dry form, also known as kibble, or wet canned form.