When a dog starts a new diet, the community of microbes in its gut changes. Wallflower bacteria multiply to dominate the scene, the old guard slipping away in defeat. As microbial species jostle for control, their metabolic byproducts, many of which are essential to Fido’s overall health, also change.
The dynamic dance between nutrients, microbes and their chemicals is well documented in dogs and other mammals, but until now scientists have only been guessing at the timing of microbial turnover. A new study by animal scientists at the University of Illinois documents that change occurs in less than a week.
“Since I’ve been researching animal nutrition, we argue about how long we should feed a new diet before we take samples, when everything is stabilized,” says Kelly Swanson, Kraft Heinz Company Endowed Professor of Human Nutrition in the Department of Animal Science and Division of Diet Sciences at the U of I and co-author of the new study. “No one has ever tested it definitively.”
It turns out that the microbes stabilize very quickly. They start making entirely new chemicals within two days of starting a new diet. And it only takes 6 days for the microbial communities to move and stabilize.
“Metabolites change very quickly, within days. The bacteria reactively metabolize and manage the substrates given to them in the new diet. Then it takes a few more days to sort out the microbial pecking order, if you will,” says Swanson. finding a steady microbiome within 10 days.”
Swanson’s team fed the dogs a common diet of dry kibble for two weeks before abruptly switching to new diets for 14 additional days. Half of the dogs ate canned food high in fat and protein and the other half ate kibble high in fiber. Meanwhile, the researchers collected poo two days after the diet change and every four days thereafter. Because science demands copy, the researchers did everything twice, switching the dogs to the opposite experimental diet the second time.
The team extracted microbial metabolites from each fecal sample, those microbial metabolism chemicals that can influence a dog’s overall health. They also identified bacterial species in faecal samples to show how the microbial community changed over time. Finally, they correlated the metabolites with the bacterial species, which had never been done before for most bacteria.
“A lot of times we feed a diet and collect feces, but there’s kind of a black box in terms of what happens in the gut. We know what certain bacterial species metabolize, but much of it is certainly unknown,” Swanson says. “Our correlations are the starting stage for linking some details, but more focused research still needs to be done.”
The primary goal was to track microbial changes at over time, but research has also supported previous findings indicating greater health benefits of a high-fiber diet compared to a high-fat, high-protein diet for dogs. These results were not a surprise, but the fact that the two extreme diets reached equilibrium in the same time frame was unexpected. For both diets, the team detected metabolite changes on day two and bacterial community changes on day six.
Swanson says the outline of the study may apply to other mammalian microbiome systems, especially those like pets and livestock that eat the same controlled diet every day. For example, the rate at which the gut microbiome responds and stabilizes after a nutritional change may be universal. And although some bacterial species and strains may differ between dogs, humans, and other mammals, metabolite/species correlations may be similar between hosts.
Is there takeaway food for dog owners? Swanson says that although her study tested a very abrupt diet change, her results support common advice to gradually switch to a new brand of dog food.
“The people generally suggest moving pets to a new diet over a seven-day period. Our study suggests that the microbes can completely change in that time frame,” he says. “When you change your diet, the body has to adapt, but the microbes have to change too. If they are not in a happy situation, you end up with loose stools or flatulence. So it’s probably good to do it a bit more. gradually at home than we did in the lab.”
This study was conducted in partnership with NomNomNow, Inc. an immediate producer of fresh pet food and health products. Nom Nom has an extensive pet health and microbiome database, which allows them to engage in a variety of studies focusing on the microbiome in the pet population.
“We are very pleased with the results of this trial,” said Ryan Honaker, Nom Nom’s Director of Microbiology. “Understanding the microbiome is central to our endeavors to improve pet health, and this study brings us even closer to discovering how the canine gut actually responds to a new diet.”