It is instinctive for dogs to eat dogtail grass, because the grass contains a lot of fiber that can help dogs digest. Whenever dogs feel uncomfortable with their gastrointestinal tract, they will eat dogtail grass to help gastrointestinal motility. This is similar to Cats eat grass for a reason, and some dogs eat grass purely out of boredom.
Tip:
Dogs lacking trace elements often have pica, and they will eat some strange things. We can improve this by supplementing trace elements.