There is a reason that dogs and cats have separate recipes and their food is not interchangeable. Here’s why you shouldn’t feed your dogs and cats the same food.
Each species has their own complex nutritional requirements. To keep things simple, cats require 41 essential nutrients (whilst dogs require 37), have much shorter digestive tracts and have a higher requirement for protein than dogs. Dogs are considered omnivorous and can synthesise nutrients such as beta-carotene from plant ingredients, whereas cats are true carnivores and can only gain these nutrients from animal ingredients.
Cats break down and replace their own body proteins very rapidly and they are unable to reduce this rate of breakdown to adapt when their dietary protein supplies are low. They are particularly sensitive to deficiencies of amino acids such as arginine and taurine. Arginine is essential for their metabolism whilst taurine is important for healthy eyes, ears, heart and immune system. Not only do cats break these down quickly, but they are also unable to manufacture their own.
Vitamins are another important area for cats. They cannot create vitamin A nor convert it from beta-carotene like dogs can, such as from sweet potato and carrots. Niacin, which is one of the B complex vitamins and is important for metabolism and skin health, can be manufactured by dogs using the amino acid tryptophan; however, the enzyme system responsible for this conversion is not very efficient in cats so they require extra in their food.
Both dogs and cats require arachidonic acid and linoleic acid. Whilst dogs are able to convert linoleic acid to arachidonic acid, cats do not have sufficient enzyme activity in the liver and therefore require high levels of animal fat as their source of arachidonic acid.
So, in summary, whilst a dog would cope with cat food for a short time, cats would develop nutritional deficiencies if fed dog food. They must be fed separate diets specifically tailored to their needs.