What makes a good diet for a cat?

Unlike most humans and dogs, the cat’s body is very highly specialised for a single purpose – hunting. As a result, they’ve lost many of the biological systems that allow them to digest a wider range of foodstuffs – so we call them obligate carnivores. Cats cannot digest plant material very well, and it is impossible and dangerous to try and feed them on a vegetarian or vegan diet.

How is this different to dogs?

Although dogs are adapted to eat meat (as are we – our intestines are almost identical!), both humans and dogs can also eat vegetables. We have the enzyme systems and capacity to obtain all the nutrients we require from plant matter (although it isn’t as efficient as eating meat, and dogs in particular are at risk of severe health problems if you try to feed a vegetarian diet without certain supplements). Cats lack these systems and cannot obtain the nutrients they need from anywhere except animal protein – which for a cat means meat.

So what exactly are a cat’s nutritional requirements?

Like all animals, cats need three different major nutrients (macronutrients) and a variety of minerals and vitamins (micronutrients).

  • Protein
    • A cat’s whole metabolism is built around eating protein. While humans and dogs can adapt to a low protein diet (although protein quality may be an issue for us too – see below), cats cannot. Protein is needed for normal cell function, muscle activity; and repair of damaged tissues.
    • It’s not just the quantity of protein that’s important – it’s the quality as well, in other words, the exact ratio of certain amino acids. Certain amino acids (including taurine, methionine and several others, some of which can be synthesised by humans) are essential and are needed for health and (in the longer term) for life itself. If the ratio of these amino acids is significantly different in the protein source compared to the cat’s body, the protein is considered low quality because more needs to be eaten to meet the essential requirements of the least common essential amino acid.
  • Fat
    • Fat is the main source of energy in a cat’s diet. It also carries the fat soluble vitamins (see below).
    • All animals need certain essential fatty acids to maintain their cell membranes, leading to health. Without them, the animal will sicken and, eventually, die. Humans and dogs can convert EFAs from plants (e.g. in evening primrose oil or even olive or groundnut oils) into usable forms, but cats lack the enzymes required to do so.
    • Fat also provides the majority of the taste of food – low fat diets are likely to be rejected by the discerning feline!
  • Carbohydrate
    • Carbohydrate is actually entirely optional for cats (they don’t actually need it at all!). It is a useful way of increasing the calories in the diet, but it isn’t essential.
    • One carbohydrate that is generally actually harmful to adult cats is lactose, found in milk. Although they need it as kittens, as adults almost all cats are lactose intolerant, and cannot digest it. This may lead to diarrhoea, but even if there are no obvious signs, high levels of lactose may lead to subtle intestinal damage (villous atrophy), so adult cats shouldn’t be fed cows’ milk, or indeed any milk unless it is certified lactose free.
  • Micronutrients – Vitamins and Minerals
    • Cats have similar vitamin and mineral requirements to other animals, but they aren’t able to process the plant forms of certain vitamins, such as vitamin A.

How can I best meet them?

Well, obviously cats need meat. But actually, they aren’t adapted to eat just meat – but whole animals, bones and organs and all (except the gall bladders which they usually reject and leave on the carpet!). This is because many of the micronutrients (especially calcium and some vitamins) aren’t found in sufficient concentrations in the muscle tissue; plus, lean meat doesn’t have enough fat to meet their energy requirements.

Cats are in fact adapted to eat whole rodents and birds, but as feeding live prey is generally considered unacceptable, and frozen mice too gruesome, the best bet is a properly formulated commercial diet.

Where can I go for more information?

If you want more information, or if you do want to prepare or home-cook your cat’s food, make sure you talk to one of our vets first as it’s harder than it seems…

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