Do you ever wonder why your dog eats grass? Is it because he’s sick and he’s trying to induce vomiting? Is he missing fiber or some other nutrient from his diet? Maybe you suspect that eating grass decreases his intestinal parasite load? Well, finally, researchers at the University of California, Davis, Veterinary Medical Teaching Hospital  are seeking answers to these questions.
Led by Dr. Karen Sueda, a veterinary resident in the clinical behavior program, the researchers devised an Internet-based survey that asked owners how frequently their dogs consumed plants, the types of plants consumed, the behavior patterns before and after eating plants, and the dog’s regular diet, as well as details of their dog’s medical and behavioral history.
For each hypothesis, they made predictions and then considered which predictions the results supported. For instance, if dogs eat plants because they feel sick or to induce vomiting, then dogs who tend to eat plants should act sick either before or after eating the plant, or should vomit after eating the plant.
This isn’t the end of the study—Sueda and her colleagues continue to investigate this puzzle. Stay tuned for updates.
Update: More than 3,000 people responded and about 68% of the usable respondants stated their dog's ate grass on a weekly basis. What's interesting is that only 8% of respondents saw signs of illness before their dog's ate grass. Of the 22% of dogs that vomited after, more showed signs of illness before ingesting the grass.
So on a final note, they concluded  that grass eating is a common behavior and doesn't neccessary indidcate illness.