British pet food manufacturers have expressed concern following a US Food and Drug Administration (FDA) investigation into links between heart disease and grain-free dog food.\r\n\r\nThe probe followed a \u201chighly unusual\u201d number in cases of canine dilated cardiomyopathy (DCM) in dogs. DCM can be fatal, weakening and enlarging the heart, leading to congestive heart failure. Symptoms of the disease include tiredness, sudden weight loss, irregular heartbeats and even fainting.\r\n\r\nLarger dogs such as Great Danes, Newfoundlands and St Bernards are most likely to contract the disease, however the FDA has said that the cases leading to the investigation were in smaller dogs.\r\n\r\nA common factor in the affected dogs was a diet heavy in legumes and potatoes, ingredients pet food manufacturers often use as a substitute for grain such as wheat, barley, oats and rice.\r\n\r\nThe UK\u2019s Pet Food Manufacturers\u2019 Association (PFMA) has said it is \u201cclosely monitoring\u201d the event in the US.\r\n\r\nDr Steven Rosenthal, a veterinary cardiologist, said: "Along with other veterinary cardiologists around the US we were starting to see a trend of boutique diets. There's been an increase in the availability of different pet foods on the market and our highly dedicated pet owners are seeking out diets that are marketed to be more healthy, grain free, sometimes even vegan diets.\r\n\r\n"There's also a population of pet owners that are feeding their dogs raw food as well. What is the link between the diet is still a question but it's a concern because we're seeing this disease in pets that aren't predisposed to these conditions."\r\n\r\nGrain-free food has recently seen a rise in popularity as independent and boutique pet food manufacturers with specialised products continuing to dominate the market.