Don’t Let Rover’s Microbiome Go to the Dogs

Dog diets influence the canine gut microbiome, particularly in obese and overweight dogs, suggesting that dietary interventions to modulate gut microbiota could help reduce canine obesity. Such interventions could include prebiotics and probiotics. [Lisa Cyr/Flickr]

Dog obesity, a growing problem, may be managed through diet and exercise—and microbiology. Although it is a less common approach to pet care, microbiology could help bring canine obesity to heel, says a team of scientists based at Nestle Purina.

According to these scientists, both human and dog obesity is related with a “dysbiotic gut microbiota.” Also, whether a gut biota is dysbiotic or, well, properly symbiotic, depends on diet. Specifically, the ratio of proteins and carbohydrates in a canine's daily diet have a significant influence on the balance of microbes in its gut.

The scientists, led by Johnny Li, Ph.D., a computational biologist at Nestle Purina, in St. Louis, MO, studied 32 Labrador Retrievers and 32 Beagles, with equal numbers of lean and overweight or obese dogs. During the first 4 weeks of the study, all the dogs were fed the same baseline diet. During the second 4 weeks, half the dogs received a high-protein, low-carbohydrate (HPLC) diet, and the other half received a high-carbohydrate, low-protein (HCLP) diet.

The results of this work appeared January 24 in the journal mBio, in an article entitled, “Effects of the Dietary Protein and Carbohydrate Ratio on Gut Microbiomes in Dogs of Different Body Conditions.” The article describes how the Nestle Purina scientists used 16S ribosomal RNA (rRNA) gene profiling to show that dietary protein and carbohydrate ratios have significant impacts on gut microbial compositions. In addition, the article recounts how the effect of diet on the predicted microbial gene network was analyzed using phylogenetic investigation of communities by reconstruction of unobserved states (PICRUSt).

The scientists found that overall, consumption of either treatment diet increased the bacterial evenness, but not the richness, of the gut compared to that after consumption of the baseline diet. Macronutrient composition, the scientist indicated, affected taxon abundances, mainly within the predominant phyla, Firmicutes and Bacteroidetes.

“The LPHC diet appeared to favor the growth of Bacteroides uniformis and Clostridium butyricum, while the HPLC diet increased the abundances of Clostridium hiranonis, Clostridium perfringens, and Ruminococcus gnavus and enriched microbial gene networks associated with weight maintenance,” wrote the authors of the mBio article. “In addition, we observed a decrease in the Bacteroidetes to Firmicutes ratio and an increase in the Bacteroides to Prevotella ratio in the HPLC diet-fed dogs compared to these ratios in dogs fed other diets.”

Dr. Li emphasized that the effects of diet on the microbiome were more pronounced in obese and overweight dogs than in lean dogs. “That seems to suggest that obese dogs and overweight dogs are more susceptible to dietary intervention,” he said.

A different diet for those animals may have a greater impact on the bacterial balance in their guts. Dietary interventions, the scientists indicated, could incorporate “prebiotics, probiotics, and other nutritional interventions to modulate the gut microbiota and to provide an alternative therapy for canine obesity.”

Although the current findings are preliminary, Dr. Li said that he hopes to see the research eventually translate into real-world ways to modify pet food. Also, the current study involved only two breeds, but Dr. Li anticipates that the findings are likely applicable to all dog breeds, “though we need more studies on other breeds in the future to be sure.”

Dr. Li pointed out that he launched the study because only a handful of previous studies have explored the gut microbiome of canines, and because the effect of diet on gut microbes hasn't been well documented. Studies on animals are lacking, but human studies have connected microbial imbalance in the gut to a variety of conditions, including obesity, metabolic syndrome, cardiovascular disease, immune disorders, and liver and brain diseases.