By: Loren W. Noblitt, D.V.M, M.S.
A lot of dogs (and some cats) eat grass. I am commonly asked, "Why does [ENTER PET'S NAME] eat grass?" - I file this question under my "if I knew the answer and how to stop it, I'd have a million dollars", category of questions. There seems to be multiple acceptable answers to this question - no one knows for sure in all cases. There are some very interesting theories to help explain our pets' 'fondness for forage', and they are as follows:
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- Boredom behavior
- Dietary deficiency
- To induce vomiting
- Biologic/Ancestral influence
1) Boredom behavior
Some dogs flat out, just like to eat grass. They like the taste and they like the texture. Some particularly like certain types of grass, like fescue grass. In these dogs there is no underlying pathology or illness causing them to eat grass. This is not true of most dogs, and, for the most part eating grass is an inappropriate behavior and justifies some looking deeper to try to see why this habit is occurring. Lack of stimulation during confinement in a particular environment, such as the back yard, can motivate a dog to eat grass or other various environmental substances. This condition, called pica is characterized by the consumption of non-nutritive material such as mulch, cat litter, grass, rocks, clothing, dirt, even feces. Pica leads to vomiting, diarrhea, and intestinal obstruction or perforation. Pica behavior can be reduced by providing your pet with stimulating and appropriate chew toys, more attention, and as a last resort: a basket muzzle.
Try not to make it a “big production” if your pet puts an inappropriate item in their mouth, as this can eventually lead to attention-seeking behavior and can fuel a pica disorder. Calmly walk over and remove the item from your pet’s mouth and replace it with an appropriate item, such as a Kong (available for both dogs and cats), Tartar Shield sticks, and Greenies. Pica can be caused by underlying medical abnormalities, therefore veterinary examination, laboratory testing (blood/urine/fecal tests, radiographs, etc.) and dietary evaluation should be explored. If your dog is eating his/her own feces (a subset of pica known as copraphagia) there are a wide array of anecdotal suggestions your veterinarian will likely have for you. Contact the veterinarians at Zionsville Animal Hospital if your dog displays this unfortunate habit!
2) Dietary Deficiency
Veterinary behaviorists and nutritionists speculate that dogs eat grass to compensate for nutritional deficiencies, iron and fiber are among the most commonly sited suspected deficiencies. A reduction in your dog’s grazing may be achieved by simply adding fresh greens and/or fibrous vegetables or fruits to their diets. Leafy greens like kale, broccoli, and parsley and pineapple have all been reported to yield favorable results. It should be noted that vegetables are most palatable (and digestible) when steamed and pureed or finely chopped before being incorporated into a dog’s meal. Additionally, dogs that eat a diet based in whole foods (which requires owners to cook meals at home) instead of commercially available, processed, non whole-food based dry (kibble) or canned foods tend to exhibit less foraging behavior.
3) To Induce Vomiting
Plant material is composed of insoluble fiber that is not readily digestible and irritates/inflames the stomach wall. Dogs seem to “know” this instinctively. Grass accumulates in the stomach instead of moving into the small intestine, like food normally would. It also can pass through, undigested, and you'll see green blades in the feces (if you look carefully enough). Underlying illnesses like Inflammatory Bowel Disease (IBD), stomach or intestinal parasite infestation, metabolic diseases of the kidneys, liver, or pancreas, and pica (discussed above) can stimulate the physiologic urge to vomit. Therefore, dogs can eat grass as a means of facilitating their own vomiting and for reducing nausea.
4) Biological/Ancestral Influence
Grass eating is a behavior exhibited by wolves. An article in the Journal of Veterinary Behavior suggests that the grass eating traits of a nursing mother can influence similar behavior in her puppies. Your dog’s mother, grandmother, and so on may be partly responsible for imparting modern-day grass eating tendencies. Conversely, another study looked at grass-eating dogs and no link was found to diet or history of gastrointestinal disease. Some dogs were reported to only eat grass if they already had an "upset stomach", and needed to vomit. Most dogs seemed to eat grass because they liked it!
As a veterinarian, I see grass-eating dogs inadvertently ingesting toxins such as fertilizer, pesticide, and other unhealthy environmental debris (particularly rocks!). Recently pesticides and some fertilizers have been linked to cancer in dogs and can cause temporary neurological problems (http://www.vet.purdue.edu/pcop/files/docs/CanineUrinaryBladderCancer.pdf).
It's not surprising that the veterinarians at Zionsville Animal Hospital recommend dog owners take appropriate measures to deter grass munching, during all stages of life, and encourage owners to explore the possibility that there is an underlying reason for it. However, there is a good possibility that the answer will be, “ Because he likes it," or, "Because the grass can't outrun him."
