Because cats are obligate carnivores , they have some very different dietary requirements compared with dogs and humans – some of these are outlined below.
Proteins are large complex molecules consisting of chains of smaller building blocks called amino acids. Cats, like all animals, require protein in their diet to provide for their needs. However, while humans and dogs can adapt to diets that have a relatively low protein content (eg, plant-based diets), cats have a much higher protein requirement in their diet that would typically only be met by feeding a meat-based diet.
In addition to requiring a much higher level of protein in the diet, cats also require a number of specific amino acids to be present – these include taurine, arginine, methionine, tyrosine etc). Without some of these amino acids in the diet, cats will simply die. These amino acids are not found in plants – many animals (including dogs and humans) can convert and use other amino acids derived from plants, but for cats health they need a preformed source of these amino acids in protein from an animal source.
Fat in the diet is a good source of energy, but also supplies fat soluble vitamins (A, D and E), enhances the palatability of food, and is a source of a type of fat called essential fatty acids (EFAs). These EFAs play key roles in maintaining the health of animals being vital in many metabolic pathways and for the integrity of the skin. Many animals like dogs and humans can convert EFAs found in plants into the EFAs that are needed in the body, but again cats require a source of animal fat with preformed animal-origin EFAs as they cannot meet their needs from plant sources.
Cats do not actually need a source of carbohydrate in their diet, and a natural diet for a cat tends to be low in carbohydrates. In contrast to many other animals, cats will derive most of their blood sugar from the breakdown of protein in the diet rather than carbohydrates. However, this does not mean that cats cannot use carbohydrate or that it should not be present in the diet, but as they have a more limited capacity to digest and utilise carbohydrates diets need to be formulated carefully.
Apart from kittens, most cats have low levels of the enzyme lactase in their intestine. This is the enzyme needed to digest the major carbohydrate (lactose) present in milk. For this reason, consumption of ordinary milk, and especially in high quantities, can often lead to diarrhoea in cats.
Again, in keeping with their adaptation to a strict meat diet, cats require preformed vitamins in their diet that are present in animals but not in plants – these include vitamin A, vitamin D and vitamin B3. However, while cats require a source of these in their diet, conversely too much of some of these vitamins can also cause problems.
Although cats clearly need meat in their diet, it is also wrong to think that they only need a source of meat. Sometimes kittens are fed a meat-only diet as they grow up, using fresh cooked meat such as chicken. Although this meets many of their dietary requirements, some critical components are still missing. It is important to remember that in the wild cats would eat a whole animal carcase (meat, organs and bones) and if fed only the meat this, among other things, is highly deficient in minerals such as calcium and will not allow the bones to grow properly.