This is a question that comes up frequently in the veterinary consult. Owners will report that their dog seems to be part cow, grazing away in the back yard on grass. Is this normal? Is their dog ill? Should they be concerned?

Let’s start by putting the worried owners mind at ease. Almost all grass eating is ok. Almost all varieties of grasses commonly available are not toxic to dogs and consuming them, even in large portions, is very unlikely to cause a problem. Some interesting poos may result, strung together on bits of grass or a grass filled vomit may result but most dogs can eat grass without any serious consequences.

But why do they do it??

Good question!

There is a range of theories as to why dogs may choose to eat grass.

1/ They feel sick – some dogs do seem to eat grass when they feel ill and do seem to vomit shortly afterwards. Studies have been done into this behaviour and no consistent link between eating grass and gastrointestinal disease has been found but it does seem to be an indicator of nausea in some dogs.

2/ Inappropriate diet – owners often worry that their grass-eating dog is not getting an appropriate diet. While it’s true that dietary deficiency can result in pica (eating inappropriate or odd items), these deficiencies have to be very marked. A dog eating at least some commercial dog food or even a half decent home cooked diet is very unlikely to have a deficiency so significant they turn to grass in serious need of nutrition. A dog that truly did have a dietary insufficiency so severe that they developed pica would very likely have multiple other signs of disease.

3/ Worms – one theory dates back to pre-domestication and speculates that dogs eat grass to de worm themselves. The theory is that the large clump of grass scrapes through the gut and pushes out any parasites. It’s hard to be sure if this is the instinct behind the behaviour but one thing is sure – a worming tablet is more effective! And dogs fully up to date with worming will often continue to eat grass.

4/ They like it –  some dogs just seem to enjoy the taste, texture or process of going out into the back yard for a quiet graze. If your dog is a happy grass eater, content to munch on the green stuff and seems to suffer no ill effects then that’s all fine. Let them graze and enjoy it! If your dog seems to only eat grass when feeling unwell then it may be worth bringing them in for a check-up. The grass consumption is not likely the cause of the illness but more likely a symptom of feeling unwell.

But for the happy grass eaters out there, we say bon appétit!