Ask the Edmonds Vet: Why does my dog eat grass?

By Dr. David Gross

My Edmonds News is pleased to introduce our newest column by Dr. David Gross, a retired veterinary science professor and author who lives in Edmonds. If you have a question for Dr. Gross, please leave it in the comment section below.

Eating grass is a behavior that every dog owner/caregiver witnesses. There are several possible explanations:

1. There is good scientific evidence that dogs descended from wolves. After generations of selective breeding, we ended up with the many different breeds of dogs available today. Genetic engineering is the same process speeded up by identifying specific genes and inserting them or removing them. However, that is another discussion for another time. Wild carnivores typically kill and eat herbivores, plant eaters. After a kill carnivores typically eat the internal organs, including the digestive tract first. This means they are ingesting partially digested plant material. Many people, including myself, believe eating grass is an attempt by the dog to respond to this ancient instinct.

2. It may be that the animal also has an instinctive desire for more bulk (roughage) in its diet. That would explain dogs that eat large quantities of grass. However, most dogs, when they occasionally eat grass eat small quantities. Perhaps they are looking for specific vitamins or minerals they are lacking. Most commercial dog foods today have everything the dog needs, so this explanation is questionable. Some grass-eating dogs nibble at the grass, chewing and then swallowing, others chomp large mouthfuls and swallow with little chewing. Not all grass-eaters exhibit the same behavior all the time.

3. Maybe the dog just develops a taste for grass and likes it. I kind of like this explanation especially for chronic grass eaters.
Some dogs will eat grass and then vomit. Is this a purposeful act? Does the dog have an upset stomach and know that if he/she/it eats grass it will result in vomiting? Hard to answer, especially since some dogs eat grass and don’t vomit. In truth dogs, if there is anything in their stomach, can vomit at will. Probably another ancient holdover from both males and females ingesting large quantities of a kill then returning and feeding their young with partially digested vomitus.

4. Dogs eat grass three days before it rains. This old wives tale probably doesn’t hold up here in the Northwest, except maybe in the summer.

5. In the Garden of Eden, all living creatures lived in harmony. There were no carnivores. All of God’s creatures were herbivores. So when your dog eats grass, it is just the manifestation of a deep seated longing for a return to innocence. Sorry about that!

A note of caution: That very lush-looking lawn — yours or your neighbor’s — may be loaded with fertilizers, herbicides and other nasties. Unless you know that the grass is safe it’s probably best to pull on the leash.

D. R. Gross graduated from Colorado State University’s veterinary school in 1960 and was in private practice for ten years. He enrolled in graduate school at Ohio State University earning a M.Sc. degree in 1972 and a Ph.D. degree in 1974. He retired in 2006 as Professor and Head of Veterinary Biosciences, at the University of Illinois, Urbana-Champaign. Dr. Gross is a Fellow of the Cardiovascular Section of the American Physiological Society. During his academic career, he published over 90 papers in refereed scientific journals and over 100 abstracts in proceedings of scientific meetings.

2 Replies to “Ask the Edmonds Vet: Why does my dog eat grass?”

  1. My 15 lb terrier eats a specific grass and smells for it in the spring, summer and fall. He prefers the young leaves. In the winter, he will eat the young leaves of my spider plant if I let him. His need for grass has increased as he ages and if he is off his food he will want to go out on the patio (often every half an hour) to search it out. Pepsid appears to relieve the problem for a day or so. I now give him half a tab 2x a day. In the winter if I’ve run out of the Pepsid he is at my patio door looking to go out every half an hour or so. This remedy was recommended by a friend’s vet for her dog who also believed that terriers were more often grass eaters. There is no doubt in my mind they eat grass to correct an acid system. I believe the grass they choose contains a soothing alkyline nutrient. I have also noticed that when he is really off his food he will ingest moregrass and ultimately vomit. There is often a yellowish colored liquid discharged along with the leaves. FYI, some vets into integrative veterinary care recommend apple cider vinegar (alkilizing to the system) for grass chewing dogs. Unfortunately I can’t get my dog to eat anything with it in it.


  2. Ms. Alexander:
    Thank you for your interesting comments. Does your dog eat small quantities or mouthfuls when he does this? It could be that he has excess stomach acid production and the grass relieves this, especially since the Pepsid seems to relieve the problem. Since vinegar is acidic it is difficult for me to understand how it can “alkilize the system”, but there are many things I have difficulty understanding. Thanks again for taking the time to comment.


Leave a Reply

Your email address will not be published. Required fields are marked *