EVIDENCE CONCERNING THE BENEFITS OF RAW FEEDING
The wolf has been used as a model by proponents of raw feeding, and much has been made of its limited capacity to digest the carbohydrate that forms a substantial part of conventional dog food. However, the domestic dog is genetically altered from its wild ancestors, with increased starch‐digesting capacity owing to different patterns of gene expression (Freeman et al. 2013). Other differences between domestic and wild canids include the balance between energy and other nutrient needs, plus longevity (Kölle & Schmidt 2015). These further highlight the limitations of attempting to closely model domestic carnivore diets on those of their ancestral wild counterparts. Furthermore, the relevance of diets eaten in the wild to the health and longevity of domestic and captive mammals may be challenged more broadly. Indeed, contemporary expertise in feeding zoo‐kept canids, including wolves, emphasises the benefit of using conventional processed dog food for the majority of the diet (AZA Canid TAG 2012).
A small number of studies have been conducted in an endeavour to provide a verifiable evidence base for some claims made for raw feeding. Faecal bacterial diversity appeared to be higher among six raw‐fed dogs compared with five fed conventionally processed food in a metagenomic study (Kim et al. 2017). A small feeding trial of boxer dogs comparing raw high‐quality beef plus supplement with a commercial dry diet and including metagenomic analysis reported smaller, firmer stools and changes (of unclear significance) in the faecal bacterial community (Sandri et al. 2017). Kittens raised on a rabbit‐based raw diet also had better stool quality, assessed with a visual grading system, than their commercial diet‐fed peers, but both groups grew similarly (Glasgow et al. 2002).
Another cat‐feeding trial compared a commercial raw diet, a supplemented raw chicken diet and a tinned diet (Hamper et al. 2017). Kittens of sequential litters from the same two parents grew similarly on any of the diets, clinical pathology analyses showed minor variations, and diarrhoea was encountered with both raw and cooked diets. Similarly, diarrhoea was neither positively nor negatively associated with raw feeding among dogs used to assist health care (Lefebvre et al. 2008). This same, year‐long, study noted significantly fewer episodes of extra‐intestinal infectious disease among raw‐fed dogs, but this was a secondary focus, using owner‐reported data and with a modest number (38) of cases. No significant difference was seen for non‐infectious disease.
A critical review by Schlesinger & Joffe (2011) concluded that the evidence advanced for the many claimed health benefits of raw feeding amounted to opinions and claims that were, at best, supported by data that was of low relevance. Claims for improved oral health in diets with raw bones find support in studies showing less calculus among feral or wild dogs and cats yet, on balance, the limited published evidence does not support claims of reduced periodontal disease with raw feeding (Steenkamp & Gorrel 1999, Fascetti 2015).
Therefore, aside from some plausible claims for better digestibility and stool quality, the various health claims made for raw feeding remain a mixture of anecdote and opinion, not backed by highly relevant data. This situation is reflected in critical reviews and in advice provided by professional bodies (Schlesinger & Joffe 2011, American Veterinary Medical Association 2012, Freeman et al. 2013, World Small Animal Veterinary Association 2015).