Nope, they're just connoisseurs of the green stuff, says Marty Becker, DVM, author with Gina Spadafori of The Ultimate Dog Lover and The Ultimate Cat Lover.
Pets love the taste and texture of grass. The newer shoots with a little water on them from the sprinklers or rain is even better.
It's like an all-you-can-eat salad bar buffet!
Sometimes dogs will consume large amounts of grass, which then propels food through the intestinal system, either back up or out the other end, so that may be the source of the myth.
They even sell living "pet grass" at the pet food chains!
My dogs just eat the back yard variety. I try to limit the amount they eat because they do tend to throw it up when they eat too much of it!
Be careful that they do not ingest poisonous greenery. My dog once ate Poison Oak at the dog park and it made him very ill and covered in hives!