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An Urban Experience
WSVA7-0468
GLOBAL NUTRITION
RAW FOODS: WHAT’S THE EVIDENCE
C.R. Bjornvad1
1University of Copenhagen, Department of Veterinary Clinical Sciences, Copenhagen, Denmark
RAW FOOD – WHAT´S THE EVIDENCE
Charlotte R. Bjørnvad, DVM, PhD, Dipl. ECVCN
Department of Veterinary Clinical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Frederiksberg, Denmark
Email: crb@sund.ku.dk
Introduction
Raw food or raw meat-based diets are defined as
“diets based on uncooked ingredients derived from domesticated or wild-caught food animal species and that are fed to dogs or cats living in home environment”1. Ingredients in raw food for pets include skeletal muscle, internal organs, and bones from mammals, fish, poultry as well as unpasteurized milk and uncooked eggs1. Raw food feeding has become increasingly popular among pet owners. Especially BARF (originally an abbreviation of Bones and Raw Food but often by supporters translated to Biologically Appropriate Raw Food) feeding has gained increasing interest. BARF is often based on raw meat- based products that are not necessarily nutritionally balanced, but are fed on a rotational schedule, thereby claimed to cover all nutritional needs of the consumer over time.
Marketing are often based on claims that these diets are more natural diets for carnivores and have superior nutritional and health benefits for the animal. Despite of these claims being unproven, they often appeal to well-intending pet owners wanting to feed their animal an optimal diet for health and longevity. In the following some of these claimed will be discussed based on the currently available evidence:
Pet dogs and cats should be fed what their non- domesticated ancestors or relatives eat because they are metabolically adapted for this diet. Both species are indeed carnivorous and the cat, as an obligate carnivore, depends on animal-derived nutrients. However, the non-domesticated relatives have a very different life compared with our pets. A recent study investigating differences in the genome of dogs and wolfs, found that several of the identified dissimilarities related directly to genes involved in starch digestion
and fat metabolism. This indicates that pet dogs have changed metabolically to a more omnivore carnivore compared with their wild relatives2. Diets that may be
suitable to support the wild relatives with a relatively short lifespan and more intensive reproductive activity may
not be optimal for supporting longevity and health in pet animals.
Commercial extruded and canned diets are unhealthy because of the processing as well as inclusion of by-products and chemically synthesized additives and preservatives. Pet food recalls during
the past years may have further spurred suspicions
for these diets being harmful. During manufacture of pet food, processing such as extrusion of dry food or heating can affect the nutritional quality in different ways depending on degree and time of heating as well as moisture content. Beneficial effects of this processing include increased plant protein and starch digestibility, destruction of anti-nutritional factors, increased amount of soluble fibre and reduced lipid oxidation. Whereas Maillard reactions, that are heat induced cross-bindings between proteins and sugars and often increase product palatability, may to some extent reduce the nutritional value and protein quality, and heat-labile vitamins (primarily B vitamins and β-carotene) may to a varying extent be lost3,4,5. However, because these are known effects of processing, manufactures are able to supplement specific nutrients following extrusion to still secure that the diet is complete and balanced. Inclusion of by-products are generally a globally sustainable
and healthy choice compared with using products appropriate for human consumption, they contain natural vitamins and nutrients that complement the diet and decreases he needs for additives.
Raw food contains natural enzymes essential for optimal digestion and intestinal function. Enzyme supplementation is generally not necessary to enable dogs and cats to digest their food and enzymes in
food will to a large degree be denatured in the acidic environment of the stomach. However, a few studies have shown that the digestibility of crude protein in
raw diets may be superior to dry food. Whether this difference is due to food related enzymes in the raw food or processing related decreased digestibility of protein
in the dry food is not certain, but one study found no differences in nutrient digestibility when the raw meat was cooked before feeding, which could indicate the latter. Furthermore, it is unknown whether this increased digestibility is of clinical relevance1.
The intestinal microbiota is important for optimal health. In humans, high protein diets have been associated
with increased risk of colonic cancer and production of Short Chain Fatty Acids (SCFA), such as butyrate seems to have a protective effect. Cats fed extruded chicken- based diets had an intestinal microbiota favouring lactobacillus and bifidobacterium compared with cats
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