Q: Why is my dog/cat eating grass?
A: There are numerous reasons that dogs and cats will eat grass and other plants.
Many dogs and cats eat grass and other plants because they just like the taste. Younger dogs and cats are similar to toddlers and tend to explore their world by putting everything including grass, rocks, and other plants, in their mouth to discover what it is and if it is edible.
Some pets will only eat grass when they have an upset stomach, and this may be an instinctive behavior. Sometimes nausea in pets causes them to try to eat or drink anything that is nearby, which results in vomiting up whatever has been consumed. In a home environment that is pet friendly, grass or other plants in our yard may be the only readily available option.
Gastroesophageal reflux disease (GERD), inflammatory bowel disease, gastritis/gastroenteritis, and other gastrointestinal diseases can be underlying causes of nausea in pets, so if your pet displays any signs of illness other than eating grass it is best to have them evaluated by a veterinarian.
An older explanation for grass ingestion is that it is an attempt to balance an incomplete/unbalanced diet that is missing key nutrients, driving a pet to seek other sources of nutrition. However, studies have not found any evidence that this is true in our modern pets. Most pets are now fed commercially available complete and balanced diets, but still try to eat grass and other plants just as often as dogs and cats who lived before pet food was readily available and affordable.
Grass may be ingested in some pets because it can act similar to insoluble fiber. Given the trend towards higher protein diets for pets this could be a real reason these days, as some pets, just like some humans, need more fiber and roughage in their diet. Cats and dogs do not have the ability to digest grass and other plants the way that cows, goats, and horses do, so the plant material just passes through from the stomach to the intestines to the colon and out again. Some think that dogs and cats eat grass to try to eliminate intestinal parasites, which may be an instinctive behavior from their wild ancestors. Longer pieces of some types of grass and plant materials can wrap around larger intestinal worms, leading to their expulsion in the stool. While cats and dogs that receive regular veterinary care are not at as high of a risk of infection with intestinal parasites like their ancestors were, the instinct is still there. Unfortunately, in some areas pets are actually at greater risk of being infected by intestinal parasites that thrive in wetter environments where grass is present, so grass ingestion can actually lead to parasite infections.
Cats are theorized to eat grass to help induce the vomiting of hairballs, but a study in 2021 did not find evidence that longer haired cats eat more grass than shorter haired cats.
Boredom could also be a reason that dogs and cats will wander around and graze on grass or other accessible plants. Humans are guilty of snacking when bored as well, though we hopefully choose more digestible options.
The real answer to this question, in many cases, may be that cats and dogs eat grass just because they can! If your pet is not showing any signs of illness, eating grass and other plants is not a behavior to worry about.
