When food is cooked the physical and chemical structure changes, this causes a number of effects:
Proteins are denatured – This means that the molecular structure of the protein is modified. This involves the breakage of the links or bonds within a protein molecule that are responsible for the highly ordered structure of the protein in the natural state. Cooking protein at high temperatures makes it virtually useless.
Fats become significantly altered – When fats are cooked at high temperatures they can become toxic. Carcinogens are released including acrolein, nitrosamines, hydrocarbons, and benzopyrene. These are all known as cancer causing agents.
Vitamins and minerals are destroyed – Up to 50% of vitamins and minerals are destroyed during the cooking process. Vitamins and minerals in their natural state are perfectly balanced; this has taken hundreds of thousands of years of evolution to accomplish. Dry dog food companies are aware of this, so after the kibble is cooked vitamins and minerals are added back to the food in levels believed to be "balanced." These synthetic vitamins and minerals will never be as sufficient as what Mother Nature intended.
All Enzymes are damaged – Enzymes are used to facilitate and regulate chemical reactions in the body, including digestion. When food is cooked all live enzymes are completely destroyed. According to Britannica a common consequence of denaturation (caused by cooking) is loss of biological activity; the loss of the catalytic ability of an enzyme.
Dogs and cats are carnivores, perfectly designed to digest and absorb the nutrients from fresh, raw meat. Raw meat and bones already have the balance that nature intended for its carnivores. This has taken millions of years of evolution. Common sense dictates that fresh food is better. No one would ever argue that processed fast food is better for you than a fresh salad. There are kibble companies out there that don’t put a ton of junk into the mix; however these kibbles are still cooked. Would you eat cooked pellets of food every day for the rest of your life? Fresh food provides the balance that nature intended and that is eaten by every other species on the planet, I don’t think that we can compete with that by adding what we believe is "balanced."
For more information, read this informative article about the findings of Francis M. Pottenger Jr who did a study comparing raw and cooked diets, involving more than 900 cats.