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Veterinary Forum November 2007 (Vol 24, No 11)

Clinical Report: Raw food diets

by Sophia Yin, DVM, MS (Animal Science)

    Although most pet owners feed their pet traditionally prepared commercial pet food, an increasing number are opting for unconventional diets, especially those containing raw meat. Diets containing raw meat can be prepared at home but also are available as commercial products that are intended to be complete and balanced.

    In addition to the hundreds of untested recipes available on the Internet, there are numerous accounts of dogs and cats that have been cured of long-term ailments after eating raw food diets. Are these diets the nutritional panacea that some people claim, or are there other factors at play?

    Lisa M. Freeman, MS, DVM, PhD, DACVN, a board-certified nutritionist and professor in the department of clinical sciences at Tufts Cummings School of Veterinary Medicine in North Grafton, Mass., sheds some light on these important questions: "Despite the many sources of funding and huge interest of many grant foundations in nutritional research, there are no scientific studies showing the benefit [of raw meat diets], just anecdotes," she says.

    According to Freeman, controlled studies would more likely reveal that properties other than the presence of raw meat are responsible for the purported benefits people may see. For instance, explains Freeman, "Owners may find that their cat no longer has signs of a lower urinary tract disorder when fed a raw food diet [and attribute it to the raw meat], when it may be the water content of the diet that is the factor of importance." The same water content, however, could be provided by feeding a cooked commercial canned food, she adds.

    Likewise, factors other than being uncooked could be responsible for apparent improvement in the skin and hair coat of pets that are fed raw food diets, Freeman says. "These diets are usually high in protein and fat, and high-fat content can improve the skin coat of some animals."

    Another board-certified nutritionist, Sally Perea, DVM, MS, DACVN, of DVM Consulting, agrees: "Owners may see improvement in their dog's health because of a single-protein source that avoids food allergy."

    To illustrate her point, Perea describes a case that presented when she was with the Nutrition Support Service (NSS) at the University of California, Davis. "Kira, a 7-year-old German shepherd, was diagnosed with exocrine pancreatic insufficiency [EPI] at 2 years of age," Perea explains, adding that the dog was being fed a raw food diet because the commercial diets that can improve EPI had caused skin allergies. The raw food diet consisted of a single-protein source that the dog was not allergic to. The NSS became involved to evaluate and balance the dog's diet. According to Perea, one of the recommendations was to cook the meat. "After the dog was fed the same food cooked, it continued to do well." The rawness of the meat was not the important factor; rather, the choice of protein and its digestibility were the important factors for this dog.

    Freeman stresses that it is important to learn why an owner wants to feed a raw food diet and to obtain a thorough dietary history so the veterinarian can address potential medical issues appropriately. For instance, owners may believe that cooked commercial diets destroy enzymes that are essential for digesting food, making these diets less digestible. However, the enzymes animals eat are themselves digested in the stomach and normally become nonfunctional. Animals rely on their body's own enzymes, which are secreted in the stomach and duodenum, to digest the food.

    Major concerns

    Both Freeman and Perea warn that major issues can be associated with raw food diets. "First off," says Freeman, "nutritional balance is a concern with any homemade diet that is not designed by a nutritionist and followed carefully." In 2001, Freeman and coauthor Kathryn E. Michel, DVM, MS, DACVN, associate professor of nutrition and chief of the section of medicine at the University of Pennsylvania School of Veterinary Medicine, published a paper in the Journal of the American Veterinary Medical Association (JAVMA) on five raw food diets — three homemade and two commercial. All of the diets, including the BARF (an acronym for biologically appropriate raw food and for bones and raw food) diet, The Ultimate Diet and the Volhard diet (Wendy Volhard's Healthy Dog Diet), had nutritional imbalances.

    "The biggest problem [found] involved calcium and phosphorus imbalance," says Freeman. Perea seconds this finding: "We saw one particularly severe case in which a kitten that presented for lameness was on a raw food diet. Radiographs showed that it had a fractured femur and pelvis attributable to osteopenia," says Perea. "We put the kitten and its two littermates, which had similar clinical signs, on a [cooked] commercial kitten diet, and within a couple of days, the generalized lameness went away." By 6 weeks, the fractures had healed and bone density had returned to normal.

    Imbalances occur even when vitamin supplements are given, such as in the raw food diet that had been fed to Kira, the German shepherd, Perea adds. The diet had consisted of 300 grams of raw beef chuck, one-third cup of boiled sweet potato, 2 tablespoons of whole milk yogurt, five frozen grapes, one-half of a banana, calcium, manganese, zinc, vitamins B12 and E supplementation and viokase powder. But the diet was still deficient in linoleic acid, calcium, selenium and iodine, she says.

    According to Freeman and Perea, a second major concern is associated with the inclusion of bones in raw food diets, which can lead to tooth fractures and gastrointestinal obstruction or perforation. Obstruction commonly involves the esophagus, but Perea recalls one German shepherd that presented with sudden vomiting, bloating and burping. "Because of chronic diarrhea, the dog had been on a raw food diet for years and had been given raw bones that morning," she says. "Radiographs showed possible obstruction, and surgery revealed chronically thickened tissue around the pyloric regions as well as a lot of ground bone that was unable to exit the stomach." Biopsy revealed inflammatory bowel disease (IBD). The diet had not only contributed to partial obstruction but had also failed to resolve the IBD.

    One of the greatest concerns about raw food diets, however, is the public health implications. Raw meat can contain pathogenic bacteria. "Many people think freezing kills pathogens, but it doesn't," warns Freeman.

    A number of studies have found bacteria in homemade and commercial raw meat diets. "In a study published in the Canadian Veterinary Journal (Joffe, 2002), [the researchers] isolated Salmonella from eight of 10 raw food diets, and three of 10 dogs were shedding the pathogen. In addition, studies have found that most of the diets are contaminated with Escherichia coli and Clostridia organisms in addition to Salmonella. One study by Finley and coworkers published in the Canadian Veterinary Journal this year found that dogs fed a single meal of contaminated raw food shed Salmonella for up to 7 days. None of the study dogs showed signs of infection," Freeman says.

    While actual clinical signs from infection may not be common, they do occur, say Freeman and Perea. A paper published in JAVMA in 2000 reported sepsis that was associated with a raw food diet in two cats. But even when clinical illness does not occur, shedders can pose a public health risk, they say.

    According to a 2006 study published in the Canadian Veterinary Journal, Salmonella spp were found in food bowls that had been inoculated with meat containing the organisms after the bowls had been cleaned with soap and water, and the contamination persisted even after they had been sanitized in a dishwasher.

    Take-home message

    Freeman and Perea say that veterinarians need to acquire a full dietary and medical history to assist owners in making a decision about whether to feed their pet a raw food diet. Owners and veterinarians can find accurate information about nutrition on the American College of Veterinary Nutrition website (www.ACVN.org). Clients who want to feed a home-prepared meal should be urged to cook the meat and should serve a balanced diet that has been developed by a board-certified veterinary nutritionist.

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