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.

While cats have been eating grass for hundreds of years, there had never been sufficient research to truly understand why they do it.

There were lots of theories, with the only scientific insight based on a study on why dogs eat grass. That was until 2019 when University of California Davis School of Veterinary Medicine — one of the leading veterinary schools in the US — conducted research into the plant eating habits of the domestic cat. The findings were published in the Scientific Journal in August 2019. My Cat Grass — a company that produces safe grass for cats that can provide many benefits — shared an in-depth analysis of the study. Here’s an overview of the findings and some myths debunked about why cats DO eat grass:

The study:

The web-based survey of cat owners, received 2,296 returns. Excluding cats that are indoor without access to plants, and cats that are outdoors where owners cannot see if they are eating plants, the main inclusion criterion was that the owner had to have been able to see the cat’s behaviour 3 or more hours a day. The resulting 1,021 returns revealed:

The data:

  • 71% of cats had been seen eating plants at least 6 times
  • 61% over 10 times and 11% never eating plants
  • Comparing cats seen eating plants at least 10 times with those never seen eating plants, there were no differences in age range, neuter status, source or number of cats in the household
  • Of cats seen eating plants at least 10 times (71%), 67% were estimated to eat plants daily or weekly.
  • When asked about how their cat seemed to feel prior to eating plants, 91% of respondents said their cat almost always appeared normal beforehand
  • Among young cats, 3 years of age or less, 39% engaged in daily plant eating
  • 27% of cats 4 years or older engaged in daily plant eating
  • Percent of younger cats showing no signs of illness prior plant eating was similar to older cats
  • Vomiting – 27% reported the cat frequently vomiting after eating plants; of which
  • Just 11% of the younger cats were observed to frequently vomit after eating plants compared to a significantly higher 30% of older cats

What does this tell us?

While this is just one study, it does suggest some key things:

  • That the myth that young cats learn this behaviour from older cats is not true
  • Plant eating is found to happen among cats of all ages, whether they were neutered or not, or how many cats there were in the household
  • Younger cats do eat plants more frequently and are less likely to vomit afterwards
  • That eating grass is not to do with cats feeling ill, most cats appeared completely normal before eating grass.

Why do cats eat grass then?

The researchers suggest that eating grass is an innate behaviour, inherited from wild ancestors to remove worms from the intestine and reduce the parasitic load (amount of parasites in the intestine).

The report says: “Studies reveal that non-digestible plants purge the intestinal system of helminthic parasites (worms). Given that virtually all wild carnivores carry an intestinal parasite load, regular, instinctive plant eating would have an adaptive role in maintaining a tolerable intestinal parasite load, whether or not the animal senses the parasites.

“Regular plant eating by domestic carnivores (cats) is a reflection of an innate predisposition (natural behaviour) of regular plant eating by wild ancestors”. [This] is supported by numerous reports of wild carnivores eating plants, as shown mostly by the non-digestible grass and other plant parts seen in their scats (cat poo)”.

What owners can do and learn?

That eating grass is not a sign your cat is missing nutrients or is not necessarily unwell. In fact, it’s an instinctive behaviour that cats are likely to exercise. So, it is a good idea to provide your cat with a safe source of grass to chew on — such as My Cat Grass.