Dogs may eat grass for a variety of reasons. For many dogs it’s considered entirely normal for them to eat a small amount of grass – in fact around 70% of dogs were found to eat grass in one study, and it was also found to be much more common in younger dogs. Some dogs, however, take grass-eating to an extreme and this could be a hint of something wrong.
What are the reasons my dog might eat grass?
The traditional theory is that some dogs use grass eating is an instinctive attempt to make themselves vomit. The grass fronds probably tickle the oesophagus (the tube that takes your food from your mouth to your stomach) as they pass through and this irritation causes vomiting. However, this doesn’t appear to be the only reason a dog might eat grass as in one study only 22% of dogs regularly vomited after eating grass, and very few of these appeared to be ill beforehand.
Some dogs seem to snack on grass, and most nutritionists and behaviourists agree that this is likely to be normal behaviour. Some people think it’s to take in micronutrients they are missing from their diet but, since grass is largely undigested by dogs and most dogs are fed complete diets rich in all the nutrients they’re thought to need, this seems unlikely. Others wonder whether it’s a way of getting extra information about a scent left on a clump of grass by another dog. It may even just be habit.
Either way, it appears to be instinctual. Wild canids certainly seem to eat grass at least as often as their domesticated counterparts. Studies of wolf and wild dog poo have shown undigested grass in their scat up to 70% of the time. There is also a new school of thought that suggests it’s a natural worming technique – the grass moves through the digestive tract unchanged and gets tangled with the worms, causing them to be passed with the grass. Unfortunately, there are no studies to suggest that this is the case or that grass would even act in this way, although we do know that chimps eat whole leaves which achieve this effect. This may also explain why younger dogs seem more prone to eating grass, as they’re more likely to carry worms.
Is eating grass harmful to my dog?
For most dogs, eating grass is an entirely normal, instinctive behaviour. In the 2008 study, no dogs seemed to have any after-effects from eating grass. However, if your dog is eating a large amount of grass there is certainly a potential for it to get stuck in the gut and cause a blockage, so I would recommend that you keep a close eye on how much your dog is eating, and if there are any signs of illness you should contact your vet.
Of course, grass that has been chemically treated with weed-killers, moss-killers and pesticides may not be safe for your dog to consume. Try to keep them away from any grass you know or suspect has been treated. Some plants are poisonous to dogs, so you should keep them away from these too. Common plants that are toxic are daffodils, lilies, onions, elephant ears and ragwort, but there are many more that could be a concern.
When should I contact the vet about my dog eating grass?
You should call your vet if you see your dog eating grass, vomiting, and then eating grass again continuously. Constant vomiting, whether because of eating grass or not, is a reliable sign that something is not quite right. Retching without producing vomit is also a concern. You should also contact your vet if your dog is eating grass instead of food, as grass is not balanced in all the vitamins and minerals your dog needs. If you see your dog eating a plant that isn’t grass, it’s probably best to identify the plant (there are smartphone apps that can help you with this, or ask the owner of the land) and call your vet for advice.
Grass can contain ticks and other parasites – if your dog is prone to having a grassy snack you should ensure their worming and tick control is up to date. Since slug trails on grass have been shown to carry lungworm, it would be sensible to ensure your dog is covered for lungworm if they often eat grass. This can only be done with prescription treatments, so I highly recommend talking to your vet to ensure you’re covered for everything.
The bottom line
The bottom line is that if your dog seems fine in himself and likes to eat grass, it’s probably nothing to worry about, but if he starts to seem ill then it’s best to get him checked out.