Why does my cat eat grass?

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Does your cat go outside and end up eating the grass? Find out why your cat might like to eat grass.

This is very common and, as far as I know, nobody truly knows the answer. There is definitely more data available from the dog world! Both domestic and wild cats eat grass and other plants. Typically, cats do not appear ill before eating plants, nor do they vomit regularly after.

It is thought that plant-eating is likely to have a biological purpose. One explanation is related to purging the worm population from the gastrointestinal tract. In chimpanzees, parts of the plants, as they pass through the digestive tract, help to increase motility and, by wrapping around the worms and getting them expelled, help keep the number of parasites down. It is possible that our cats’ ancestors developed the same strategy, and what we observe today is an old way of clearing the system.

Occasionally, I have a feeling that cats eat grass when they don’t feel quite right, possibly having some gastrointestinal discomfort and trying to address it. Some of these cats vomit after eating grass, commonly with a hairball. Hairballs can be a sign of gastrointestinal disease. Therefore, we should investigate further if we find them more than infrequently.

Many cats will eat grass and never show any signs of illness or vomit after. I am not sure what the reason is for that! It may be that there is no disease association or that the disease is not obvious, such as with a mild form of inflammatory bowel disease or food sensitivity.

The take-home message is: ensure your cat has access to plants that are safe to eat, and avoid plants treated with chemicals. If the frequency of grass-eating changes — or there are other signs of illness — please speak to your vet.