Fecal bacterial composition of dogs fed with kibble (KD) versus raw meat-based diets (RMBD) when data were analyzed based on individual dogs (A,C) or dietary groups (B,D). The relative abundance of fecal bacterial community composition at (A,B) phylum and (C,D) genus levels.
Only the top 10 phyla or genera are depicted for clarity. n = 27 for KD and n = 28 for RMBD.
Credit: Frontiers in Veterinary Science (2024). DOI: 10.3389/fvets.2024.1328513
In recent years, the practice of feeding dogs raw meat-based diets instead of kibble has grown, in part because raw meat does not require heavy processing or include binders and preservatives that could negatively affect a dog's health.
Common advice for humans is that a diet rich in unprocessed plant-based foods is best. Among its health advantages are anti-inflammatory benefits that promote heart and gut health, and a lower risk of diseases, including cancer.
Similarly, some proponents of raw meat-based diets for dogs believe that such regimens reduce the risk of gut health issues, support better dental health, and protect against inflammatory conditions. Nowadays, ads promoting the practice of feeding fresh and raw food diets to dogs are ubiquitous in print and media.
But some veterinarians caution against raw pet food diets. Raw food can contain bacteria that may cause diseases in pets who consume the food, as well as in humans who handle and prepare it. Studies have documented that such bacteria may be resistant to antibiotics. Additionally, raw food diets created by pet owners may be nutritionally imbalanced; a 2022 study found nutrition deficiencies in over 90% of dogs on a raw meat-based diet within its study group.
With such considerations as a background, a U.S. research team from Oklahoma State University and the University of Florida has conducted the first study to evaluate how canine feeding regimens might affect anti-inflammatory markers in the gut. Their work appears in Frontiers in Veterinary Science.
Within cells, metabolites are small molecules (those of low molecular weight) that are responsible for metabolism and cellular function, maintenance, and growth; these comprise a cell's metabolome. Food intake is among many factors that affect metabolism, and through metabolomic profile screens, researchers can test generally for inflammatory disease.
The researchers of this new study compared inflammation in dogs fed kibble-based diets (KD) vs. raw meat-based diets (RMBD). The paper states, "We hypothesized that dogs fed RMBD would have alterations in their microbiota and metabolome that correlated with changes in fecal and systemic inflammatory markers."
The study population included 55 clinically healthy adult dogs, all weighing more than 9 kg, who had been either fed a kibble-based (n = 27) or raw meat-based (n = 28) diet for longer than one year, according to their owners. Because many owners reported occasionally offering their dogs human food, leftovers, and dog treats, the researchers placed both groups on restricted diets for 28 days before beginning their testing; "either a single brand of kibble (Purina Pro Plan Savor) or RMBD (Titan Blue, Ross Wells) and a single ingredient treat," the study explains.
The research notes that starch comprised approximately one-third of the KD group's food consumption, while starch represented less than 1% of what the RMBD group consumed due to an absence of dietary plant sources. However, each group ate similar amounts of protein; 3.6 g/kg bwt/day for the RMBD group and 3.2 g/kg bwt/day for the KD group.
The dogs remained with their owners for the duration of the study, and the owners recorded the dogs' weekly food consumption, with instructions to report any deviation from the prescribed study diets. On day 28, the dogs returned to the lab for physical examination and collection of blood and stool samples.
Findings
The team found similar inflammatory markers—including serum metabolites specific to antioxidant and anti-inflammatory functions—in the blood samples of both groups, but significantly different results in the two groups' intestinal inflammatory markers. They also observed differences between the groups' metabolomes and fecal microbiota.
In the RMBD dogs, the researchers found higher levels of fecal IgA (a mucosal antibody that protects against infection), IgG (an antibody that protects the immune system against previously encountered bacteria and viruses), and IAP (another gut-protecting antibody).
"We theorize these increases in RMBD fed dogs may reflect improved gastrointestinal homeostasis and immune function as well as increased feed digestibility," they write.
However, they were unable to determine whether the observed differences were beneficial or not, due to the study's short duration and inclusion of only healthy dogs. They had expected to find a parallel between the differing fecal inflammatory marker results and systemic inflammatory marker results, but did not, and suggest that this could result from a low level of biomarker sensitivity.
As next steps, the researchers suggest that larger studies of longer duration, including more sensitive markers—functional assays—might shed more light on the effects of the two diets. They also note that with respect to intestinal inflammation, a study design exposing the same dogs to both diets could reveal the effects of each.
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