Center for Companion Animal Health, UC Davis
CCAH Update, Fall 2001
Dietary Taurine Deficiency and
Dilated Cardiomyopathy in Dogs
Dilated cardiomyopathy is a heart disease that results in an enlarged (dilated) heart with impaired ability to contract and pump blood.
Dr. Andrea Fascetti and Dr. Robert Backus check blood sample preparations before running an assay for taurine levels.
Dilated cardiomyopathy (DCM) is one of the most common acquired cardiovascular diseases in dogs.
In cats, a diet deficient in taurine clearly results in DCM, but in dogs, the need for dietary taurine has not been generally recognized because dogs are known to be able to synthesize taurine from the sulfur amino acids cysteine and methionine.
Yet, during the past two years, veterinary nutritionist Andrea Fascetti and her colleagues Quinton Rogers and Robert Backus documented low plasma taurine concentrations in dogs with clinical signs of DCM. Some animals died‹the prognosis is poor for dogs with this disease‹while some survived when given supplemental taurine and supportive care.
The cause of taurine deficiency in the canine DCM cases was not readily apparent, yet the common factor was diet history. Some of the dogs had been eating home-made diets, while others were eating similar commercial diets‹the diets appeared sufficient in protein and sulfur amino acid content, and had passed testing in accordance with Association of American Feed Control Officials (AAFCO) feeding trials for all life stages.
These cases and findings in several pilot studies suggest that diet does affect taurine metabolism in dogs and may play a role in the development of DCM.
Recent evidence also suggests that taurine stores and the development of DCM may be affected not only by diet, but also by a dog's size. There is a prevalence of DCM in families of dogs and specific breeds, many of which are large and giant breeds.
Dr. Backus found evidence in a study of Newfoundland dogs with taurine deficiency to support the idea that taurine metabolism may be influenced by "metabolic" body size, which takes into account that the amount of energy needed by the body is correlated with total body surface area, not just body weight.
For example, calculations of metabolic body size indicate that the caloric and protein intake per unit of body weight in a large breed dog is actually lower than in a small breed dog.
Dr. Fascetti is currently investigating the influence of both diet and metabolic body size on taurine metabolism in small and large breed dogs.
Information from the studies will contribute to ongoing and subsequent research on taurine metabolism in dogs, and will help clinicians interpret taurine profiles to make appropriate therapeutic recommendations.
Dr. Fascetti hopes these studies will increase veterinarian and client awareness in order to prevent diet-related DCM and to improve the life expectancy of dogs afflicted with the disease.
Dr. Fascetti and her colleagues are carrying out a variety of investigations to find out how diet composition affects taurine metabolism in dogs, and how taurine deficiency may play a role in the development of DCM, particularly in large-breed dogs.
Dr. Fascetti and her clinical nutrition resident, Dr. Sean Delaney, have begun a scientific survey to determine normal ranges for plasma and whole blood taurine concentrations in dogs‹reference ranges for taurine concentrations in cats are known, yet healthy ranges in dogs have not been determined. Understanding normal ranges for taurine is essential to understanding the factors that affect taurine metabolism in dogs and the link between taurine deficiency and DCM. Blood samples will be collected from client-owned animals along with each dog's age, breed, weight and other measurements, medical history and a complete diet history. The effect of metabolic body size and diet on the taurine
levels will be determined.
Last year Dr. Backus found diet-associated taurine deficiency and cardiac insufficiency in more than half of a group of 21 privately owned Newfoundland dogs, which excreted extraordinary amounts of taurine in their urine. Drs. Backus and Fascetti are now planning a larger project to estimate the prevalence of a possible widespread taurine deficiency in the Newfoundland breed. Non-invasive clinical tests and feeding trials will determine if taurine deficiency in Newfoundlands might result from 1) a reduction in protein digestibility, 2) a diminished capacity to synthesize taurine from sulfur amino acids, or 3) loss of taurine in urine. Pedigree analysis may reveal a genetic basis for taurine deficiency.
Another breed susceptible to DCM is the Doberman pinscher. In a three year project funded by the Doberman Pinscher Foundation of America, Royal Canin, Morris Animal Foundation and the CCAH, graduate student Dr. Cristina Torres is working on developing a taurine-deficient adult dog model that can be used to further study DCM in humans and animals. Dogs in the study are given purified diets and monitored for taurine concentrations and cardiac changes. Upon depletion of taurine, the dogs are supplemented with taurine until their physiology returns to normal. The study investigates possible causes for taurine deficiency and will determine the quantities of dietary taurine and sulfur amino acids needed to prevent DCM in purified and commercial diets.