Guest Contributor— Answers Chief Veterinarian, Dr. Doug Knueven, veteran among veterinarians, examines raw nutrition as a healing power of pets and works to ensure an all-encompassing true health (physical, mental and spiritual) regimen in veterinary medicine for animals.
Probiotics and the intestinal microbiome are hot topics these days.
Research on these subjects are poring in from the scientific community and it can be difficult to know how to apply this information to improve the health of your pet. To add to the confusion, there are commentators who, either through their own misunderstanding of the research or due to their desire to sell a product, twist the conclusions of certain studies.
A case in point is the study, “The gut microbiome correlates with conspecific aggression in a small population of rescued dogs (Canis familiaris).” https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6330041/
I have recently seen articles implying that this research shows that Lactobacillus bacteria, like those found in fermented dairy, cause aggression. The commentaries conclude that it is dangerous to give your dog fermented milk products. A superficial look at this study by anyone who is unfamiliar with the subtleties scientific literature might lead to such a misinterpretation. So, let’s dive into this study with scientific eyes and see what it is really saying. We’ll look at some key lines from the study to come to a better understanding.
From the “Results” section of the study we read, “The family Lactobacillaceae was more abundant in aggressive dogs, while the family Fusobacteriaceae was more abundant in non-aggressive dogs…” If this were the only line you read from this multi-page study, then I could understand being suspicious of fermented dairy which contains lots of Lactobacillaceae bacteria. However, the line just before this one states, “Specifically, Proteobacteria and Fusobacteria manifested higher relative abundance in non-aggressive dogs, while Firmicutes was relatively more abundant in aggressive dogs.” So, the association was not just with Lactic Acid bacteria. It could be that certain combinations of bacteria are associated with aggression. Also, different species and strains of species within Lectobacilllaceae can have very different biological effects. This study did not differentiate the bacteria to that level.
Now let’s go back the basis of the study. From the “Materials and Methods” section we find, “A single fecal sample was collected from the kennel of each of 31 pit bull type dogs residing at a temporary shelter while in protective custody.” The researchers then corelated the behavior of the dogs to the bacteria found in their stool. From a scientific standpoint, 31 dogs is a low number from which to draw conclusions. Also, one stool sample from each dog may not fully represent their microbiome. In the Abstract, the researchers themselves admit that this is a small sample size. Furthermore, they were certainly not looking at typical pet dogs and none of these dogs were receiving any probiotic supplementation. This study has nothing to do with dogs consuming fermented dairy products.
Finally, a well-known truism within the world of scientific research is that “association does not prove causation.” For example, it has been observed that people who are found walking around on college campuses carrying calculus books score higher on IQ tests. From that information it does not follow that if you want to improve your IQ, you should get a calculus book and walk around on a college campus. Similarly, there could be other factors involved in the association between certain gut bacteria and aggressive behavior in dogs.
The study that needs to be done to prove causation is to take a large group of non-aggressive dogs and, under a double-blind, placebo-controlled condition, give half the group one specific strain of Lactic Acid bacterial probiotics. If the behavior changes, then you have suggested causation. When that experiment has been repeated several times with the same outcome, you have reasonably proved the hypothesis. Until then, there is only inuendo.
Every scientist will tell you that it is unwise to draw any firm conclusions and base your behavior due to any one, small study. From my work with using Answers fermented dairy products in the treatment of hundreds of pet dogs over the past decade, I am confident that these real foods do not adversely affect behavior. The value of probiotics was discovered by the observation that people who consumed fermented foods were healthier than those who did not. It makes sense that fermented foods are a superior source of probiotics to any pill or powder.