Appropriate macronutrient balance for small animal diets

I found the article “Awareness and evaluation of natural pet food products in the United States”¹ to be interesting, but I worry that statements in the article might be interpreted as arguing against feeding high-protein, low-carbohydrate foods to dogs and cats.

With regard to diets for dogs, the authors cite a study² that found genetic evidence suggesting that dogs have a greater ability than wolves to digest starch and suggest that these findings indicate that “as domestication progressed, dogs evolved the capacity to thrive on starch-enriched diets.” However, even if dogs can digest starch better than wolves can, it does not necessarily follow that dogs thrive on starch-enriched diets. There is evidence that predators select foods on the basis of the macronutrient balance that enhances their survival.³ A recent study⁴ that examined the selection of macronutrients by adult domestic dogs of five diverse breeds found that the dogs consistently preferred a diet that included 7% of metabolizable energy from carbohydrates. This would be considered a low carbohydrate content, compared with the carbohydrate content of most commercial diets commonly fed to dogs. The authors of that study⁴ concluded that “the recent rapid divergence among dog breeds is not substantially reflected in their macronutrient priorities compared with other phenotypic features such as size, color, and temperament.”

As for cats, after citing several studies demonstrating the health risks of high-carbohydrate diets, Carter et al¹ state, “However, there is currently limited evidence to suggest that moderate amounts of carbohydrate in the diet (20% to 30% of metabolizable energy from carbohydrates) are detrimental to the metabolism or health of cats.” This statement appears to suggest that there is at least some evidence that moderate amounts of carbohydrate in the diet may be detrimental to cats. I propose that future studies attempt to determine the optimal level of dietary carbohydrate to promote health, rather than the maximal level of dietary carbohydrate that cats can survive on. To that end, studies of the macronutrient balance that domestic cats select may be instructive. A meta-analysis⁵ of studies reporting on the feeding habits of feral and stray domestic cats found that the daily energy intake of nitrogen-free extract (essentially carbohydrates, starches, and sugars) was only 2%, and the authors⁵ state, “The calculated nutrient profile may be considered the nutrient intake to which the cat's metabolic system has adapted.”

The balance of macronutrients in the diets of dogs and cats plays an important role in their health. In my opinion, the notion that pets benefit from diets with moderate levels of carbohydrates for cats and high levels of carbohydrates for dogs is insufficiently supported by the current body of evidence.

Douglas Knueven, dvm

Beaver Animal Clinic Beaver, Pa

In-home euthanasia versus hospice

The recent JAVMA News article “The end-all practice: home euthanasia”¹ brings much-needed attention to in-home euthanasia as an option for families seeking end-of-life care for their pets outside of a hospital setting. While Dr. Cooney's work is excellent and is raising the standard of care for in-home euthanasia practices, I take exception to the comment that “[e]uthanasia work doesn't require a lot of medical knowledge and has flexible scheduling.” In-home euthanasia practice may indeed allow for part-time work or flexible scheduling, but I would be disappointed to find it being marketed as a veterinary practice option for those with limited medical knowledge.

The statement does, however, highlight an essential distinction between in-home euthanasia services and hospice care. “There are no hours in hospice” is something I frequently hear myself saying to families of my patients. I suppose scheduling is as flexible as you make it but would argue that client support is far more time-consuming in hospice care than in traditional veterinary practice.

More importantly, hospice care is not for those lacking medical knowledge. An understanding of normal aging, the interplay between complex medical conditions involving multiple organ systems, available treatment options (curative, palliative, and otherwise), the anticipated biological behavior of various disease processes, multimodal pain management techniques, techniques for in-home nursing, and best practices for communicating with referring veterinarians, specialists, and their staff is a basic requirement for practitioners in this area. When veterinary students tell me they are interested in providing hospice care, I encourage them to complete a rigorous internship, spend a lot of time doing emergency work, surround themselves with good mentors, and learn everything they can about cutting-edge curative treatments. Then, they should think about the alternatives to hospice care.

I appreciate that the JAVMA News article focused on in-home euthanasia services. However, in-home euthanasia is not hospice, even though these end-of-life services are inextricably linked within our profession (and even though hospice can include euthanasia). Although in-home euthanasia and hospice are frequently discussed as if they are interchangeable, they are not, and we should make a distinction between in-home euthanasia and comprehensive medical disciplines such as hospice and palliative care. It is my sincere hope that as these areas of practice evolve, all veterinarians will consider themselves active providers of compassionate end-of-life care for their patients as well as liaisons to trusted social workers and related resources for their clients.

Katherine Goldberg, dvm

Whole Animal Veterinary Geriatrics & Hospice Services, PLLC Ithaca, NY

Feral cat policy is about more than cats

In their recent letter to the editor, Weedon et al¹ advocate for changes to the AVMA policy on free-roaming abandoned and feral cats,² suggesting that the current policy does not accurately reflect emerging research findings. We question, however, whether the science and facts that inform the current policy have really changed. Feral and free-ranging cats kill substantial numbers of small mammals, birds, reptiles, and amphibians every year³ and compete with native wildlife for prey. Outbreaks of hookworm infection and typhus at sites where dense populations of feral cats, rats, and fleas coexist are serious human public health problems.⁴ Feral cats remain the most common rabid domestic animal, and exposure to rabid cats leads to postexposure prophylactic treatment of more humans than exposure to any other species.⁴ Rabies vaccination of feral cats does not reduce the incidence of postexposure prophylaxis or the associated public health risks and costs.⁴ Cats are the only known shedder of Toxoplasma oocysts, which are increasingly recognized as causes of waterborne and point-source community outbreaks. Toxoplasmosis is a devastating disease in a wide array of marsupials, sea otters, and other marine animals and poses a health risk for many species that generally do not ingest raw meat. An increasing body of evidence is implicating it as a factor in several serious human behavioral, neurodegenerative, and dementia conditions.^5,6

Weedon et al¹ cite studies showing that trap-neuter-vaccinate-return (TNVR) programs can be an effective means of controlling feral cat populations but fail to cite studies documenting failure of TNVR programs when maintained over longer periods or in larger areas.^7,8 At the Stanford University campus, where a TNVR program was started 30 years ago, there are still as many feral cats, and many other locations have seen no reduction in 10 to 20 years. Relocating cats to start new colonies, as practiced by many advocates of trap-neuter-return, only compounds the problem. We hope all veterinarians and cat advocates will respect community members who don't want to deal with the health, safety, financial, wildlife, and ecological consequences of community cats.

Arguing whether feral cats are as healthy as owned cats is, to our minds, missing the point. Outdoor cats die prematurely of a variety of causes, and while weight and body scores may be indicators of health, they do not provide information on quality of life. Public funds spent on TNVR programs could, we believe, be better spent promoting and enforcing mandatory spay-neuter provisions and adopting out homeless cats. As a profession, we are emphasizing responsible pet ownership and more frequent examinations and telling clients that cats are safer and healthier indoors. How does this square with TNVR programs for cats living outdoors?

We strongly believe that TNVR does not serve one health goals or the welfare of feral cats or wildlife or advance public health.⁹ As veterinarians who work on a wide array of species, we welcome a review of the AVMA's feral cat policy and trust that review will be guided by good science and reflect the large array of concerns and species the veterinary profession serves.

Kirsten Gilardi, dvm

Davis, Calif

Colin Gillin, ms, dvm

Corvallis, Ore

Cheryl B. Greenacre, dvm

Knoxville, Tenn

Robert Groskin, dvm

Teaneck, NJ

David A. Jessup, dvm, mpvm

Royal Oaks, Calif

William B. Karesh, dvm

New York, NY

Douglas Mader, ms, dvm

Marathon, Fla

Marcy J. Souza, dvm, mph

Knoxville, Tenn

Peregrine L. Wolff, dvm

Reno, NV

Michael Ziccardi, dvm, mpvm, phd

Davis, Calif

Meg Sutherland-Smith, dvm

San Diego, Calif

Expanding the idea of one health

One health has been defined by the AVMA as “the integrative effort of multiple disciplines working locally, nationally, and globally to attain optimal health for people, animals, and the environment.”¹ There are other definitions, but all recognize that issues relating to health, the environment, and society cannot be resolved unless they are approached holistically. The one health concept is particularly relevant to the veterinary medical profession because, unlike the human medical profession, it tends to view human life in relation to other living things and the environment.

The profession's current one health initiatives focus on public health, zoonotic diseases, and food safety, but they tend to overlook unique opportunities for the veterinary profession in addressing global challenges related to hunger, malnutrition, poverty, and food insecurity. The website of the One Health Initiative,² for example, fails to mention agriculture, food production, food systems, or the livestock industry, even though all of these are fundamental to human health at a time when the global population is growing rapidly and some 800 million people, 1 in 9 among us, suffer from hunger, malnutrition, and related diseases.

Most of the hungry live in developing countries where they face unprecedented threats to their survival from climate change and poor nutrition. According to the State of the World's Children (UNICEF 2007), 10.9 million children under five years of age die in developing countries each year. Malnutrition and hunger-related diseases cause 60% of the deaths, nearly 18,000 a day. Many of the hungry live in rural areas of the developing world, where almost 1 billion poor subsistence farmers keep livestock³ and, to a great extent, depend on their animals for their health and survival.

Agriculture in general and livestock farming in particular inevitably cause environmental damage. Owing to rising urban demands for meat and milk and the uncertainties of global warming, the problem in developing countries, already acute, is worsening. Farmers need information and resources to control diseases and intensify production sustainably. Veterinary interventions and extension services are badly needed to confront these problems.

In view of these unparalleled challenges, we suggest that the one health movement should evolve to encompass agriculture, economics, food systems, nutrition, and the cultural and political environments in which disease, hunger, and poverty persist. All of these issues are intertwined in complex, dynamically changing ways. More research, better metrics, better understanding, and better communication with farmers are sorely needed.

Because veterinary medicine has broad responsibility for animal health and productivity, environmental health, public health, and nutrition, the profession, under the one health umbrella, is equipped to assume a leading role in developing integrative policies that can ensure a sustainable food system and reduce hunger in the world.

James Ferguson, vmd, ms

Professor of Nutrition

David Galligan, vmd, mba

Professor of Animal Health Economics

Robert Marshak, dvm

Dean Emeritus

Alan Kelly, bvsc, phd

Dean Emeritus

School of Veterinary Medicine University of Pennsylvania Kennett Square, Pa