Let's Dish on a Dogs' Digestive System & Microbiome - Part 1
The topic of canine nutrition is directly associated with dogs' digestion. Making sure your pup has all the nutrient requirements to live a happy and healthy life is essential to understanding their digestive system and nutrient absorption from an evolutionary standpoint.
If you have not read it yet, I recommend you check out these two great blogs first: Canine Plant-based Nutrition: It's Time for Evidence written by Katherine Kramer, DVM, CVA, DABVP and Vegan Dogs: Research and Reasons by Virchew's founder, Laura Simonson. Both are excellent resources for plant-based canine nutrition and to help understand the evolution of a dog's ability to digest plants and starch!
Now, let's dive into our furry friends' digestive system!
Basic Dog Digestive Details
The gastrointestinal (GI) tract in dogs includes the esophagus, stomach, and intestines. In humans, the digestive process begins in the mouth. We grind our food with our teeth and moisten it with saliva containing carbohydrate digestive enzymes (amylases).
Dogs, however, do not chew their food as they do not have any amylase in their saliva. Instead, they eat it up quickly to carry it straight to the stomach, where the digestion begins. Gastric protease and lipase are produced in the stomach to break down protein and fat into smaller molecules that the body can absorb.
The esophagus bridges the mouth to the stomach as part of the chewing process. The esophagus walls are comprised of strong muscles, which push the food down into the stomach.
Gastric acid and enzymes are released in the stomach, where the process of digestion begins. Dogs' gastric acid is 100 times stronger than humans, allowing them to break down proteins into smaller amino acids and bone matter. Once partially digested, the food leaves the stomach and enters the small intestine.
The Small Intestine
The small intestine is approximately two and a half times a dog's total body length. In dogs, this organ has three parts. The first section is attached to the stomach in the duodenum. The liver and pancreas release enzymes and other digestive secretions through ducts connected to the duodenum. The middle portion (jejunum) is the longest and where your dog's body absorbs the nutrients from their food—the remaining passes by the ileum, attached to the large intestine.
The Large Intestine
The large intestine represents the final portion of the digestive process. It is larger in diameter than the small intestine, and its primary role is to absorb water and accumulate and eliminate waste products from your dog's body.
The Role of the Microbiome
The gut microbiome is colonized by trillions of bacteria, fungi, and other microorganisms that live in humans' and animals' GI tracts. The gut microbiota is very responsive to nutrients in the diet, particularly the macronutrient content (fibre, starch, and protein). The bacterial element is the biggest and contributes to essential digestive functions and immune system modulation.
There are different types of bacteria species that reside in the GI tract. Some ferment fibre and carbohydrates, while others are proteolytic. The abundance of gut-friendly bacteria in dogs is reliably measured in the fecal microbiome. For example, one clinical study found that dogs fed a specific diet for 32 weeks had their microbiome quickly restore itself to its baseline after returning to the control diet. Species diversification is essential for microbiome resilience as it indicates a healthy microbiota.
It is worth mentioning that many diseases are associated with alterations in the gut microbiome impacting its functions, commonly known as dysbiosis. These changes in the microbiome have significant effects on immune function and intestinal inflammation. One of the mechanisms in which gut dysbiosis increases inflammation is the lack of the beneficial species responsible for producing anti-inflammatory molecules, such as short-chain fatty acids and indoles.
The content of fibre, starch and protein in a dog's diet has a significant impact on the gut microbiome than the source of the ingredients (animal or plant) if the macronutrient composition is similar.
The Importance of Fibre
Now that you got a quick introduction to the gut microbiome, let's dish on the role of fibre in your dog's digestive tract. Aside from keeping our furry friends regular, fibre can also help with weight management, blood sugar stability, digestion, and other fantastic health benefits for your pup.
Fibre is, of course, only available in plant foods as part of the cell walls. There are two types of fibre: water-soluble and insoluble. To avoid episodes of diarrhea or constipation in your dogs is crucial to have a balanced amount of both types of fibre. Healthy dogs should eat high-quality foods that contain both soluble and insoluble fibre to gain the benefits of both.
1. Insoluble Fibre
Sources: cellulose, hemicelluloses, and lignans.
They are not digested in the GI tract.
Help dogs with weight management by increasing the volume of food they can eat without adding extra calories.
Adds bulk to the fecal matter which can stimulate movement within the GI tract. This mechanism can help dogs experiencing constipation.
2. Soluble Fibre
Sources: chicory, inulin, fructooligosaccharides, pectins, psyllium, plant gums, oats, beet pulp, and some fruits and legumes.
Bacteria in the large intestine break this fibre down into short-chain fatty acids with many health benefits.
They are also considered prebiotics, food for 'good' bacteria in the gut. Adequate amounts of soluble dietary fibre in the diet are significant to your dog's immune system and overall health.
Beta-glucans - Promising research on one type of soluble fibre
What makes beta-glucans special?
Beta-glucans are water-soluble plant fibres consisting of chains of up to 2,000 glucose units in beta form. They are present in the cell walls of bacteria, fungi, yeasts, and some plants.
There is exciting and recent scientific evidence in the literature of the role beta-glucans have in modulating immune function in the body of humans and dogs. Most studies on beta-glucan use its isolated forms as an additive to strengthen a dog's immune system.
Different immune cells in the intestinal wall identify free beta-glucans as a pathogen-associated molecular pattern. This recognition increases the activation of immune cells and the production of cytokines, resulting in the most effective immune response possible, which prevents infections.
It is common for obese dogs to show a decrease in immune function, which decrease resistance to infections. However, the use of compounds like beta-glucans is promising in animal nutrition. This topic is fascinating, and there is an excellent opportunity to explore its benefits in improving animal health and potentially reversing (or preventing) diseases like cancer.
Foods rich in beta-glucans:
shiitake and reishi mushrooms
After reading this blog, I hope you are as excited as I am about dogs' gut microbiome and the role of powerful plant foods for dogs! It is empowering to know that what we feed our four-legged friends can dramatically impact their overall health. Like humans, a diverse gut microbiome is adaptable and resilient and plays many roles in promoting health.
Hungry for more? Watch for Part 2 of this series where I will serve up details about Virchew's Love Bowl ingredients, their digestibility and more!
Oh, and make sure you check out a few Virchew digestion and tummy testimonials here!
ABOUT THE WRITER
Tatiana Victorino is Virchew's Lead - Operations & Research. She received her BSc in Food Engineering at UNICAMP, an internationally recognized center of academic excellence in Brazil and also holds a BCIT Operations Management certificate. With over 5-years of professional experience working in the food and beverage manufacturing industries, Tatiana has gained dynamic expertise in process design and improvement, lean manufacturing, business operations, quality assurance, and research and development. Tatiana's background is invaluable as she works with Virchew's Veterinary Partnerships, nutrition programs and product R&D. Got a question for Tatiana? She would love to hear from you. Email her at email@example.com
Gut microbiome of dogs and cats: https://www.sciencedirect.com/science/article/pii/S0195561621000127?via%3Dihub
Facts about dogs’ digestion: https://www.petmd.com/dog/nutrition/7-interesting-facts-about-your-dogs-digestive-system
b-glucans in dog food: https://www.researchgate.net/publication/330838173_Beynen_AC_2019_Beta-glucans_in_dog_food
Oats and b-glucans: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6067736/