The iconic image of a kitty with milk-stained whiskers, licking its lips with delight, has to be one of the most stereotypical animal-food relationships, among other joys such as a donkey with a carrot, a cow with a buttercup or a safe of ducks harassing the elderly for a loaf of bread. (Yes I did have to check the term for “a group of ducks on land”…). However, is milk good for cats? Or, of even greater concern, is it bad for cats?

Why can’t some cats drink cow’s milk?

Kittens thrive off their mother’s milk. In the first few days post-birth, they drink the mother’s colostrum; this high-protein initial milk of lactation contains many “maternally-derived antibodies”, which help the young kittens’ immature immune systems. After this, the mother produces milk, which is of lower protein content.

At around four weeks of age, kittens typically begin the weaning process, and after that start to enjoy the delights of mice and tins of food which look better than the average student’s dinner. When a kitten stops drinking milk, it may stop producing the enzymes necessary to break down and digest milk; lactase, necessary to digest lactose (get your vowels right!).

When the cat no longer produces this, it means that milk cannot be digested, and can cause diarrhoea. The milk can remain in the gastrointestinal tract undigested; bacteria in the gut capitalise on this energy substrate, causing fermentation, gas and abdominal pain for the unsuspecting cat. The particles of undigested milk can also induce an “osmotic diarrhoea”, which essentially draws water into the gastrointestinal tract.

Diarrhoea is a risk to a cat’s health due to potential damage to the gastrointestinal tract, a loss of fluids which can cause dehydration, and loss of appetite which can cause a negative energy balance. Of further concern is the loss of ions and electrolytes necessary to maintain your cat’s healthy cells and organs. In short, diarrhoea should be avoided where possible; one such way is in not giving them cow’s milk.

‘My cat has never had a problem; are all cats lactose intolerant?’

No, not all cats are lactose intolerant. However, the crude way to test whether a cat is lactose intolerant would be by giving it milk and seeing it produce diarrhoea. Beyond the obvious welfare implications, this is not a pleasant task to clean, as any vet student having done their stint in a cattery will tell you!

For cats capable of digesting milk, we need to be careful about keeping them trim; one saucer of milk is a lot for a cat, and a high-fat content can lead to our feline friends becoming a bit more ‘cuddly’ than may be healthy for them! This is a particular concern for less active cats, such as the elderly or house cats.

In short – try to feed a diet that is suitable for an adult cat, not a little kitten!

‘My cat adores milk, I think it will upset her not to get a saucer of her favourite thing…’

If your cat is a milk-fiend, there are alternatives. When trying to entice our rescue cat to like me (hasn’t worked yet), I could often be found coaxing her for a cuddle with special “Cat Milk”; this tends to have more calcium, less lactose and be high in protein. Whiskas, TopLife and Pets at Home all do brands of special milk for cats. Fazing out giving dairy milk for the feline-friendly formulations is likely not to be met with protest!

Make sure he or she has access to clean, fresh water at all times, and try to avoid milk!

“Cats will amusingly tolerate humans only until someone comes up with a tin opener that can be operated with a paw”- Terry Pratchett

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