Dogs eating grass is an "instinctive behaviour" and no one knows exactly why they do it, a vet has said.
Pete Wedderburn, vet columnist for the Daily Telegraph, explained that he thinks dogs eat grass because they enjoy it - the same reasons why they like pet toys.
The vet had been contacted by a reader whose Wheaten Terriers eat grass whenever they go on walks and then the undigested grass hurts them when they pass it a few days later.
Dr Wedderburn wrote: " My own feeling is that dogs just do it because they like doing it, in the same way as they enjoy chewing toys.
"No grass will ever be digestible for dogs: they’re not herbivores. Perhaps you could grow a patch of finer, less irritating grass for them in your own garden."
He added that you can buy "cat grass", which may be suitable.
Cats eat grass because it trigger a regurgitation reflex in them, which helps to expel indigestible matter, such as hairballs.