By Sophie Hazelden

Obese dogs who lose a significant amount of body weight using a specific weight management diet show changes in their faecal microbiota, that typically supports previous research in humans.

Obesity is always a hot topic in the human and animal world, with increasing numbers of small animals reported as obese over the last few years. Canine obesity is considered a serious metabolic disease that is associated with greater risks of developing other illnesses such as diabetes, cardiovascular diseases and some forms of cancer, like the risks seen in humans. Given the detrimental effects of obesity on the welfare of both canines and their owners, investigating changes associated with obesity and how we can prevent it, is of high interest within veterinary research.

The term microbiota refers to the specific microorganisms, including bacteria and fungi, that inhabit an environment, such as the gut or faeces. Scientists have previously investigated the role of the gut microbiota in obesity within humans and dogs. These studies have found that obesity is associated with changes and disruption of the gut microbiota, specifically, seeing a decrease in biodiversity. Bacterial biodiversity can be measured based on species richness, which is the number of different bacterial species in an environment, or species evenness, which describes the relative abundance of each species within the environment.

Research has recently been carried out into the changes in faecal microbiota of dogs during their weight loss journey. The research included client-owned dogs (mix of breeds) that were obese and had been referred to the Royal Canin Weight Management Clinic at the University of Liverpool between June 2009- August 2017. All dogs were clinically healthy, with no signs of gastrointestinal disease and had not received antibiotics in the month before admission. Of all the dogs that met the criteria, 20 completed the full weight loss program and met their target weight, these dogs had faecal samples collected at the start and end of their weight loss journey. Five additional dogs were included that had faecal samples taken at the start of their weight loss and then 15 days later at the first follow up visit. For the dogs completing the full weight loss journey (average of 331 days) all dogs were fed a dry food that was specifically for weight management (Canine Satiety ® diet, Royal Canin; one dog was also fed a wet food version).

Analysis of the faecal samples taken at the start of weight loss showed that the dogs age, sex and neutered status did not significantly affect measures of faecal microbial species richness or evenness. To ensure changes in bacterial composition were due to losing weight rather than the feed, faeces from five dogs sampled at the start of their weight loss journey and only 15 days later, were analysed. These dogs showed no significant differences in bacterial composition when the feed had been supplied but they were still significantly heavier than their desired weight, this was also supported by separate research.  The dogs that successfully reached their desired weight showed significant increases in faecal microbial richness and evenness after weight loss, consistent with previous research. Whilst most changes seen were in accordance with human studies into obesity, one important difference in the core bacterial composition between humans and dogs was the increase of the phylum (a level of classification), Fusobacteria. In humans, Fusobacteria is associated with colon cancer, however in dogs, it appears to play a role in maintaining health- decreasing in abundance when gastrointestinal diseases are present and increasing in abundance after weight loss, being associated with leanness in dogs. This, along with other key findings in the research carried out, shows that after weight loss using a weight management diet, the bacterial population changes to be within the range deemed normal for clinically healthy dogs. 

For more information please read the full research paper click here

Sophie Hazelden

Sophies is in final year of a PhD looking into the effect of zinc oxide and rearing environment on pig gut microbiome and their immune response. She has a keen interest in investigating the microbiome across monogastric species.