Diet-related Dilated Cardiomyopathy in your Canine Companions

Akshaya Chandrashekar

FVC Executive 2018-2020, OVC Class of 2024

What is Dilated Cardiomyopathy?

Dilated cardiomyopathy (DCM) is a condition characterized by the enlargement of the cardiac chambers that debilitates the ability of the heart to pump blood. As the condition progresses, fluid collects in the lungs, and often leads to heart failure (Case, 2018). Certain breeds of dogs, particularly larger ones such as Doberman Pinschers and Great Danes, are genetically predisposed to the condition, whilst others may have increased susceptibility for diet-related reasons. The lack of an important amino acid, taurine, has been associated with the condition but the mechanisms of how this contributes to the development of DCM is still under investigation.

What is Taurine?

Taurine is a sulfur-containing amino acid synthesized from 2 precursor amino acids, methionine and cysteine, in the central nervous system and liver (Kaplan et al., 2018). It is not incorporated into proteins but is found circulating freely in the blood and in tissues (Case, 2018). It is abundant in the brain, retina, muscle tissues and many other organs. It is also an essential component of bile acids which are released into the gut and used to emulsify (break down into small droplets) fats in food (Hofve, 2019). It is the most abundant free amino acid in the heart and as such, is thought to have a significant role in heart health, including modulation of calcium fluxes necessary for heart muscle contraction (Kaplan et al., 2018).

Diet, taurine-deficiency, and DCM;

Although large and giant breeds of dogs tend to produce taurine at a slower rate than smaller breeds, endogenous production is normally sufficient. It was thought that because dogs can meet their own taurine needs endogenously, supplementation is not required as is with cats (Case, 2018; Tôrres et al., 2003). In 1995 however, a veterinary cardiologist showed that a subset of dogs with DCM were taurine deficient (Tôrres et al., 2003). Successive studies demonstrated that with supplementation, many of the heart changes could be fixed (Tôrres et al., 2003). Golden retrievers and American cocker spaniels dominated in these cases, suggesting some breed-specific susceptibility to developing taurine-deficiency (Tôrres et al., 2003; Hofve, 2019). Specific lines of spaniels and retrievers cannot make sufficient amounts of taurine and hence, tend to develop a taurine-dependent form of DCM (Hofve, 2019).

Although DCM is one of the most described clinical manifestations of taurine-deficiency, taurine deficiency also is associated with many other conditions including impaired reproduction, growth restriction, central nervous system dysfunction, ocular blindness, and spinal deformities (Kaplan et al., 2018). With the exception of breed-specific weaknesses in taurine synthesis, canines are usually able to synthesize sufficient amounts of taurine when its precursors are present in adequate amounts within the diet (Tôrres et al., 2003). Studies have found an association between taurine deficiency and commercial lamb-meal and rice diets, particularly in dogs typically not prone to developing a taurine-dependent form of DCM (Tôrres et al., 2003). In addition to lamb having a moderately low level of sulfur-containing amino acids, it is theorized that the poor protein digestibility of some lamb-meals limit the bioavailability — the proportion that enters circulation once introduced into the body — of the precursor amino acids required for taurine synthesis and increase the fecal-loss of taurine (Kaplan et al., 2018; Tôrres et al., 2003).

Additional investigations into dogs with DCM revealed an increased frequency of diets consisting of kangaroo, duck, buffalo, salmon, bison, venison, lentils, peas, fava beans, tapioca, barley, or chickpeas as the major ingredient (Freeman et al., 2018). These diets are characterized as boutique, exotic and grain-free (BEG) and it may be their grain-free nature that gives rise to the apparent link between this type of low taurine diet and DCM (Freeman et al., 2018). Exotic ingredients have different nutritional characteristics and digestibility than regular chicken diets, influencing the normal metabolism of important nutrients in canines (Freeman et al., 2018).

In July 2018, the U.S. Food and Drug Administration (FDA) Centre for Veterinary Medicine launched an investigation into this potential link between the development of canine DCM and grain-free diets. Initial studies found that dogs with DCM that had been eating a grain-free diet, had more advanced heart failure changes compared to those eating a grain-based diet (Freeman et al., 2018). Possible causes that are being explored include absolute deficiency of taurine and other nutrients, altered bioavailability of nutrients and the unintentional addition of toxic ingredients (Freeman et al., 2018). In addition to taurine, BEG diets could also be deficient in important ions and vitamins such as copper, choline, L-carnitine, magnesium, thiamine, vitamin E, or selenium, all of which play important roles in normal cardiac function (Freeman et al., 2018).

What can you do for your pet?

The FDA is continuing to investigate the relationship between taurine- deficiency, diet and DCM to identify the causal mechanisms of canine heart failure. Their current recommendations for dogs with suspected diet- associated DCM include changing the diet to one consisting of standard ingredients such as chicken, beef, corn, and wheat (Freeman et al., 2018).

For dogs that require special dietary consideration due to other existing medical conditions, a consultation with a veterinary nutritionist is advised to provide the best possible combination of nutrients for your canine companion (Freeman et al., 2018). Additionally, providing taurine supplementation for individuals that are deficient is crucial as it can reverse cardiac changes and improve function (Freeman et al., 2018).

The heart of the matter is that no conclusions can be made, as of now, about the underlying dietary mechanisms of taurine-dependent DCM. However, given what is known, it is suggested that owners feed their dogs a diet that contains suitable levels of high-quality, animal-sourced proteins.

Most health conditions your pet could face can be prevented by exercising good nutrition. Watch what you are feeding your furry companions to give them the best possible quality of life!

References

Case, L.P. (2018, August 15). DCM in dogs: taurine’s role in the canine diet. Retrieved from: https://www.whole-dog-journal.com/food/dog_food/dcm-in-dogs-taurines-role-in-the-canine-diet/

Freeman, L.M., Stern, J.A., Fries, R., Adin, D.B. & Rush, J.E. (2018, December 1). Diet-associated dilated cardiomyopathy in dogs: what do we know? Journal of American Veterinary Medical Association. 253, 1390-1394. doi: 10.2460/javma.253.11.1390

Hofve, J. (2019, November 3). Taurine, dog food, and heart disease in dogs. Retrieved from: https://www.onlynaturalpet.com/blogs/holistic-healthcare-library/taurine-dog-food-and-heart-disease-in-dogs-1 

Kaplan, J.L., Stern, J.A., Fascetti, A.J., Larsen, J.A., Skolnik, H., Peddle, G.D., Kienle, R.D., Waxman, A., Cocchiaro, M., Gunther-Harrington, C.T., Klose, T., LaFauci, K., Lefbom B., Lamy, M.M., Malakoff, R., Nishimura, S., Oldach, M., Rosenthal, S., Stauthammer, C., O’Sullivan, L., Visser, L., William, R. & Ontiveros, E. (2018, December 13). Taurine deficiency and dilated cardiomyopathy in golden retrievers fed commercial diets. PLOS One. 13(12). doi: 10.1371/journal.pone.0209112

Tôrres, C.L., Backus, R.C., Fascetti, A.J. & Rogers, Q.R. (2003, September 22). Taurine status in normal dogs fed commercial diet associated with taurine deficiency and dilated cardiomyopathy. Journal of Animal Physiology and Animal Nutrition. 87(9-10), 359-372. doi: 10.1046/j.1439- 0396.2003.00446.x