Your dogs could be eating a silent killer, and you are buying it for them.

Researchers have started to notice a link between grain-free dog food and a condition known as DCM (dilated cardiomyopathy ) or an enlarged heart. Dogs appear fine, and then one day they are not.

Normally DCM mainly affects large dogs, but it has recently been seen in dogs like Labs, retrievers, whippets and mixed breeds -- none of which are considered genetically predisposed to the disease. The link: grain-free dog food.

Unfortunately, to be able to diagnose DCM your dog has to have an echocardiogram.