Why are domestic cats lactose intolerant? Well, there comes a time when a mother decides to wean her kittens. Kittens rarely wean themselves. The mother prevents her kittens having access to her milk. The kittens come hungry and seek alternative food sources.
In the meantime the mother brings back prey to the den and tears it up so that it is easier for her kittens to eat. Up until this point the kittens’ digestive tract is geared up to digest mother’s milk. Milk sugar is lactose and an enzyme, lactase, breaks it down.
When milk sugar is substituted for the sugars in muscle the kitten develops an alternative enzyme called sucrase to break it down. Lactase has been substituted for sucrase whereupon the kitten is no longer able to digest milk.
Lactose intolerance means that when a cat ingests lactose it can cause diarrhoea, gas, cramping, bloating and feeling sick.
This in turn can lead to the cat feeling sufficiently unwell to be apathetic. The same thing can happen to people too. For people, lactose intolerance is caused by an insufficient amount of lactase leading to lactose staying in the digestive system where it is fermented by bacteria causing the symptoms mentioned above for cats – the symptoms are the same.
There is another aspect to this: many people are also intolerant to cow’s milk. Cow’s milk is meant to be drunk by cows and not by humans. I always drink lactose free milk because if I don’t, the cow’s milk irritates my sinuses so that if I catch a cold I invariably develop a secondary bacterial infection in my sinuses. Since drinking lactose free milk this has hardly ever happened. I wonder if some cats are both lactose intolerant and cow’s milk intolerant?
For centuries domestic cats have been fed cow’s milk! I immediately wonder how many millions of hours have elapsed during which domestic cats have felt apathetic and ill simply because their owner fed them cow’s milk. A great shame and a blot on the copybook of centuries of domestic cat welfare but at the time people simply were unaware.
There are many paintings, posters and photographs of cats drinking milk and even today there are probably millions of people putting down milk for their cat when really it is not the right thing to do. Cats like milk, even though it is not good for them, because of the fat content. Fat is high in calories for energy. It’s about survival.