The microbiome is more than notable to veterinary medicine – it is thought to impact the immune system, liver function, brain, digestion, appetite, inflammation, and hormone balance.
Since the idea was floated to pay attention to the metabolic performance of all microorganisms colonizing the human body, since they have about 100 times more genes than the same human body, the microbiome has been the focus of science.
The microbiome includes viruses, bacteria, archaea and fungi. Most bacteria are commensals, some are even symbionts, and very few are pathogens. The functions of these bacteria are extremely diverse: they break down food components and produce vitamins, short-chain fatty acids, amino acids, neurotransmitters, bacteriocins, antifungals, antiviral substances, alcohol and endotoxins.
In addition, bacteria deconjugate and dehydroxylate bile acids, steroid hormones and drugs and can influence their metabolism and action.
Bacterial DNA has now been detected in almost every organ. The effect of bacteria on the immune system, liver function, brain, digestion, appetite, inflammation, hormone balance, bone formation, muscle regeneration, insulin resistance, kidney function and heart is currently the subject of intensive research.
The intestinal microbiome is best studied, which varies in composition depending on the section of the digestive tract.
The intestinal microbiome of mammals is dominated by five phyla: Firmicutes, Bacteroidetes, Proteobacteria, Actinobacteria, and Fusobacteria.
Cats, dogs and humans even show a similar distribution of bacterial classes.
Dysbiosis of the Gut Microbiome
A disturbance of the microbiome is called dysbiosis. As a result, diversity and individual groups of bacteria are reduced; others, such as pathogens, have been able to increase disproportionately.
Dysbiosis leads to the impaired metabolic performance of the microbiome and thus to inflammation, reduced nutrient cleavage and reduced vitamin production.
Approximately 50 to 80 percent – depending on the species – of the lymphatic apparatus is located in the intestine; this tissue is referred to as the Mucosa Associated Lymphoid Tissue.
Along with the microbiome, the mucus and the intestinal epithelial cells, the MALT is part of the three-layer intestinal barrier.
Dysbiosis and the Intestinal Barrier
The mucus layer overlying the intestine protects the body from harmful environmental influences and pathogenic germs and from too intensive contact of the immune system with the intestinal microbiota. While the outer mucus layer contains many bacteria, including commensal bacteria, a thin inner mucus layer is virtually sterile.
Specific surface molecules of the bacteria can activate different immune cells and trigger a massive release of pro-inflammatory cytokines. Thus, an overgrowth of pathogenic bacteria or even an immigration of bacteria into the innermost mucus layer can lead to a general pro-inflammatory status of the immune system.
On the other hand, Dendritic cells are antigen-presenting cells. They can take up bacteria or bacterial components and present them to T cells, mediating either immune tolerance or an immune response.
While TH1 and TH2 cells are responsible for a cellular and humoral immune response, regulatory T cells can be considered their counterparts as they secrete anti-inflammatory IL-10 and IFN-β.
In the healthy gut, they constitute the majority of T cells.
Dysbiosis not only leads to damage of the intestinal epithelium by pathogenic germs but can also lead to inflammatory reactions due to direct activation of the immune system.
Dysbiosis candamage the intestinal barrier and thus lead to increased permeability of the intestinal wall – a so-called “Leaky Gut” has developed.
Diseases and the Intestinal Microbiome
Adverse changes in the intestinal microbiome can be found in many diseases – this is not limited to intestinal diseases, but also obesity, Diabetes Mellitus Type 1 and Type 2, depression, Parkinson’s disease, rheumatoid arthritis, neurodermatitis, liver cirrhosis, sepsis and chronic renal failure are all associated with a Dysbiotic Gut Flora!
In Dogs and Cats, research is currently focused on the digestive tract; however, some studies have also shown alterations in the gut microbiome in chronic renal failure, atopy, gastric distention, obesity, exocrine pancreatic insufficiency, FCoV infection, and FIV infection.
Whether these microbiome changes are the cause or consequence of the disease has not yet been conclusively determined. Research into the gut microbiome is still in its infancy and is still a largely unknown world for science.
Nutrition and the Gut Microbiome
Many influences affect the microbiome of dogs, first and foremost, the diet. Many studies have shown the influence of different rations in dogs and cats, which differ in protein, carbohydrate, and fiber content.
In particular, a diet rich in prebiotic fiber appears to positively affect the gut microbiome, as this prebiotics provide a nutrient base for “good” gut bacteria.
But drug use away from antibiotics must also be considered. A 2018 study published in Nature showed a direct antimicrobial effect on approximately a quarter of all drugs tested
Prebiotics & Probiotics
One characteristic of a healthy intestinal flora is the diversity of its microbes. The more diverse the microbial community, the more resistant it is.
When there is a variety of good bacteria in the gut, there is less room for harmful bacteria to colonize permanently.
Environment, genetics and other factors affect the microbiome. But diet determines which microorganisms reproduce best and win the battle for space and resources.
The most effective way to support a dog’s gut microbiome is to provide a wide variety of dietary fiber in the long term. Prebiotics act like fertilizers in the intestines. Namely, these indigestible carbohydrates (dietary fiber) feed healthy microorganisms in the dog’s gut.
Probiotics are usually added after antibiotic therapy in capsule form or as an additive in dog food to influence the composition of the dog’s intestinal flora positively.
Data are becoming thinner for chronic diarrhea, although one study found a comparable effect of prednisolone and a multistrain probiotic on clinical and histologic parameters — moreover, long-term administration of the probiotic eliminated dysbiosis.
A small number of research papers exist on atopic dermatitis, chronic renal failure, FHV infection, and megacolon. However, due to the often poor quality of the studies and heterogeneity in dosage and choice of probiotics, Science can draw no definitive conclusions.
A look at human medicine provides an impetus for further research topics on the use of probiotics in veterinary medicine for obesity, halitosis, diabetes mellitus, NAFLD, atopic eczema, irritable bowel syndrome, and inflammatory bowel disease.
Fiber in plants consisting of long-chain carbohydrates, or selectively fermented feed additives that lead to improved gut microbiota, and have health benefits
Nutrient substrate for microorganisms
Living microorganisms that are supposed to have a positive effect on the intestinal microbiota, either in capsules or in food
Prebiotics combined with probiotics, which have a positive influence on the composition of the intestinal flora
Mixture of prebiotics and probiotics
The Intestinal Microbiome is a largely unknown world for science – but research has shown the importance of a balanced gut flora in many diseases.
Diet is a major influence on the microbiome, and prebiotics, probiotics, and synbiotics can all be used to support a healthy gut microbiome.
The Dog’s Microbiome and how it is influenced by diet, lifestyle, and medications represents a new factor to consider in veterinary medicine as well, revealing new therapeutic approaches.
Further research is needed to determine the most effective use of substances – like Probiotics and Diet to improve your Dogs Health.