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Wednesday 16 October 2019

Dogs and cats eat grass - but why do they do it?

Pete's terrier Kiko seeks out and eats green blades of grass
Pete's terrier Kiko seeks out and eats green blades of grass

Pete Wedderburn - Animal Doctor

On our daily walk this morning, my little dog Kiko stopped and did something strange: she started eating grass. There was some new growth of green, leafy blades of grass beside the path, and she stopped and began to eat it hungrily. She must have eaten half a handful of grass before she was willing to move on. I've also seen my pet cats eat grass: they seek it out and chew it, just like Kiko did today.

Why do carnivorous pets eat grass? What's going on inside their heads? I'm often asked these questions, and they are not easy to answer. Like many odd types of animal behaviour, we can only make educated guesses at the reasons. Animals cannot talk to us and explain their thinking.

But by watching what they do, and trying to rationalise it, we are able to come up with reasonable theories to explain why meat eating animals might want to graze.

The first, and most likely, explanation, is simply that animals like doing it, for no particular reason. Pets are inquisitive creatures that enjoy exploring their environment, and since they can't use their hands, they do this with their mouths. So it's common for dogs and cats to lick and chew things around them. And when they have a quick chew of fresh grass shoots, it's likely that they find that they enjoy the taste and texture, so they do it some more. In most cases, it's probably as simple as that.

There are, however, a few other theories that are worth mentioning.

First, animals may have some instinctive need to devour grass for its nutritional value. Grass contains fibre, so perhaps pets sometimes feel that they want some more fibre in their diet: eating grass is an obvious answer. Grass also contains vitamin C, and although pets can produce this internally as part of their normal metabolic processes, there's an argument that they may have some sort of urge to top this up by eating grass.

Second, grass can sometimes cause pets to empty their stomach by regurgitating or vomiting. The ingestion of vegetation can irritate the stomach, and it's possible that pets realise this at some level, so they can cause themselves to be sick by eating grass. Certainly, there is a link between some pets feeling nauseous, and subsequently eating grass then being sick.

I remember a terrier called Shelley who was a repetitive grass eater, and it was strongly associated with gastric upsets. In her case, the gastric upset came first. Her owner would notice that Shelley's stomach started to rumble loudly, and Shelley would then become frantic to go outside. Once in the garden, she would head straight for a patch of unkempt grass, and she'd chew frantically at this. Soon after, she would vomit, and she'd then stop eating grass, and be happy to go back indoors. We discovered that if her owner gave her regular stomach settling medicine, she'd stop having the rumbly tummy, and she never wanted to eat grass.

In general, grass eating is a harmless habit that owners don't need to worry about. There are five areas where there may be some concerns.

First, in cases like Shelley, where grass eating is excessive, leading to an exacerbation of signs of illness. Sometimes, owners of pets like this are advised to prevent dogs from over-doing the grass eating in such cases, by applying a basket-muzzle when their pet goes outside to grassy areas.

Second, in some dogs, grass eating can lead to digestive upsets further down the digestive tract. Grass cannot be digested by dog and cat digestive systems, so it passes right through their system, emerging intact at the other end. The most obvious problem happens when some pets have difficulty passing faeces because long, fibrous grass has become tangled in their faeces, preventing it from being passed smoothly. Owners sometimes have to put on a glove and gently pull the grass-snared faeces from their pets' back passage. Rarely, a visit to the vet may be needed for an enema to remove the grass.

Third, when dogs eat grass, they often also swallow tiny slugs and snails that happen to be on the grass at the time. These can carry a nasty parasite called lungworm that can cause serious illness in dogs. If your dog is a regular grass eater, you should talk to your vet about regular preventive lungworm treatments.

Fourth, when a pet eats grass, swallows it and then regurgitates it, it can end up stuck at the back of the nose, inside the nasal chambers, causing fits of sneezing. This is more common in cats than dogs. When it happens, the grass needs to be physically removed, which sometimes means a short anaesthetic is needed.

And finally, if grass has been sprayed with weedkiller or pesticide, it has the potential to be toxic to pets. The simple rule is to follow the instructions on any chemical applied to grass, and if necessary, keep pets well away from treated areas. And if you are visiting an areas where grass may have been treated by someone else, keep your pets away from it.

For most pets, occasional grass eating causes no harm, and is nothing to worry about. Just as humans often enjoy chewing on an occasional blade of grass, why shouldn't pets?

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