Beginning a few years ago, veterinarians and veterinary cardiologists in particular began to see a common form of heart disease occur in dogs eating certain food brands and homemade rations.
What made dilated cardiomyopathy, or DCM, unusual in this case was that it was occurring in a nonhereditary fashion.
Prior to this, the condition was well known and documented extensively in certain breeds. DCM is a cardiac muscle disease that results in a decreased pumping efficiency by the heart.
What causes DCM exactly is still up for debate. A number of factors including nutritional, infectious and genetic predisposition have been implicated. But because DCM occurs at a higher incidence in specific breeds that suggests a heritable genetic component.
Most experts agree however that the disease occurs because of several things, or a multifactorial etiology.
Before the feed ration question arose, the breeds known to be predisposed to DCM included the doberman pinscher, the great Dane, the boxer and the cocker spaniel. Once the issue of diet popped up on the radar in other breeds, it wasn’t long before nutritionists zeroed in on the amino acid carnitine. More specifically, they saw that a carnitine deficiency may play a role. Later, a deficiency in the amino acid taurine was noted, too.
So out of all the things to suspect, how did they decide on carnitine and taurine? It’s because previous research and clinical observation showed a carnitine deficiency responsible for some cases of boxer DCM. And aligning with Koch’s postulate, they also identified that some cases of DCM were responsive clinically to adding back the right amount of taurine in cocker spaniels. That became known as taurine-responsive DCM. Taurine is a sulfur containing amino acid.
Wait a minute, carnitine and taurine? Yes, I understand the confusion so hang on for just a bit. Taurine, unlike other amino acids, is typically not incorporated into proteins. It is however found in its highest concentrations inside cardiac muscle, skeletal muscle, the central nervous system and platelets. This tiny molecule is involved in a wide variety of metabolic functions including normal heart muscle function.
The type of carnitine discussed here is a small water-soluble molecule. Dogs get carnitine either from dietary protein, or from synthesizing it in their liver using essential precursor amino acids. Synthesis also requires iron, vitamin C and vitamin B6 to make the synthesis reactions work. This form of carnitine is not used for protein synthesis.
Dog’s hearts receive as much as 60 percent of their energy by oxidizing long-chain fatty acids. As this metabolism occurs, carnitine is necessary to shuttle along the energy components to where they need to be. It also has a buffering function keeping reactions working properly and avoiding cellular damage. Finally, it helps take out some of the metabolic trash after reactions occur.
The bottom line is all dogs need sufficient amounts of both amino acids in their diet in a form they can extract from the food. For a variety of reasons, the most important of these functions may be normal cardiac function and cardiac muscle health.
Some formulations of pet foods did not, and still may not, have the necessary quantities in an available form and some heart disease resulted.
Dog owners don’t need to become veterinary nutritionists to figure this out. What they need to do is choose a dog food that is labeled “complete and balanced” on the package to ensure its quality. Second, they should choose a food that has been tested extensively in feeding trials.
Finally, they should consult a veterinarian about their pet’s nutrition.
Charlie Powell is the public information officer for the Washington State University College of Veterinary Medicine, which provides this column as a community service.