I am always on the lookout for research studies concerning raw diets for dogs and cats. A lot of claims are made about the health benefits of raw diets, but there is no substantive body of evidence to justify these claims. In particular, claims that raw diets are healthier than commercial dry or canned pet foods are common, despite no clinical studies making this comparison. I hope eventually such studies will be done, and while I am skeptical raw diets will prove superior, I will be happy to start recommending them if they prove to have benefits that outweigh their risks.
Unfortunately, a recent study of raw diets doesn’t add much information directly relevant to the debate.
Beloshapka, AN. et al. Effects of inulin or yeast cell-wall extract on nutrient digestibility, fecal fermentative end-product concentrations, and blood metabolite concentrations in adult dogs fed raw meat-based diets. American Journal of Veterinary Research 2012;73(12):1016-1023.
The study compared raw beef and chicken-based diets with or without a couple of prebiotics (not probiotics) in research dogs. All dogs were fed each of the diets, and measurements were made of body weight, fecal consistency, nutrient digestibility, and fecal chemicals associated with the presence of prebiotics.
The short version of the results is:
- The diets were highly digestible (though previous studies have suggested commercial and cooked fresh diets are also highly digestible, and no clinically significant effects on health have been shown to be associated with any differences in the digestibility of these different forms of pet food.
- Over the three weeks of time on each diet, all of the dogs remained healthy on all of the diets.
- The beef-based diet varied more than expected from the predicted nutrient composition, likely due to variation in the nutrient profile of individual ingredients. This is a big problem for homemade diets generally, which are not nutritionally consistent and aren’t monitored for any nutrient excesses or deficiencies on an ongoing basis as commercial diets are.
- Fecal consistency (but not amount) varied with diet composition, but feces were normal for all dogs on all diets.
- Fecal volume was lower than previously reported for dry commercial diets, though again the relevance of this for health hasn’t been established. Given the risks of raw diets, feeding them just to have less poop to pick up doesn’t seem sensible.
- The prebiotics increased the levels of certain compounds in feces, as they have previously been shown to do. This is hypothesized to have health effects, but these have not been demonstrated.
- Skin and coat quality did not appear to be affected by diet.
- Interestingly, the mean urine specific gravity on all of these diets was greater than 1.046 for all diets. This is highly concentrated urine for dogs, suggesting potentially inadequate fluid intake. Interestingly, another study from the same institution, one comparing fresh cooked and raw diets with dry kibble in cats, also found unusually concentrated urine, and no difference between raw/fresh and dry diets. This certainly isn’t consistent with the claims that one benefit of raw diets is greater moisture content and less work for the kidneys.
It is not clear from this report whether or not the diets were formulated to be nutritionally adequate as defined by AAFCO standards, though levels of calcium and phosphorus were reported to be within acceptable limits (though variable based on the specific ingredients in each of the diets). Obviously, nutritional adequacy would be an important issue in evaluating the quality of any diet.
So overall, this study shows that raw diets are highly digestible (which is not surprising, but of questionable importance), that short-term feeding of them under controlled circumstances doesn’t seem to have any negative effects or any benefits unless one considers less poop an important benefit or buys into the still unproven health benefits of prebiotics. There is nothing wrong with studying the variables this project looked at, of course, but it doesn’t have much direct bearing on the controversy over feeding dogs and cats raw diets.