Gut Health and Behaviour in Puppies and Adult Dogs
Updated: 3 days ago
When a dog seems anxious, unsettled or harder to train than usual, we often look at their routine, their walks or their training first, and those all matter. But there's another part of the picture that's easy to forget, and that's the gut. The gut and the brain talk to each other all the time, and what's going on in your dog's tummy can affect how they feel and behave. There's never one diet that fits every dog, so here's how gut health and behaviour are linked in puppies and adult dogs, and simple ways to support both, with your vet on board.
THE SHORT ANSWER
The gut and brain are connected through nerves, hormones and the immune system, a link known as the gut-brain axis. The gut is home to trillions of bacteria, called the microbiome, which help with digestion, immunity and the production of chemicals that affect mood, such as serotonin. When the gut is upset, dogs can feel uncomfortable, sleep badly and cope less well with stress, which can show up as restlessness, irritability, reactivity or trouble focusing. Signs of gut problems include loose stools, wind, tummy gurgles, grass eating, licking surfaces and changes in appetite. To support gut health, feed a consistent, good quality diet, change food slowly, protect sleep and keep stress low. If your dog has ongoing tummy problems or a sudden behaviour change, ask your vet before trying supplements.
What is the gut-brain axis?
The gut-brain axis is the two-way communication system between the digestive tract and the brain. Messages travel along the vagus nerve, through hormones and through the immune system.
The gut also produces many of the chemicals that affect mood. A large share of the body's serotonin, often called the "feel-good" chemical, is made in the gut. So when the gut isn't working well, it can affect how a dog feels as well as how they digest food.
The microbiome
The microbiome is the community of bacteria and other microbes living in the gut. A healthy, varied microbiome helps break down food, supports the immune system and keeps the gut lining strong.
Stress, illness, antibiotics and sudden diet changes can all upset it. When that happens, dogs may have tummy problems, feel uncomfortable and find it harder to settle.
Gut health in puppies
A puppy's gut is still developing in the first months of life. Puppies pick up bacteria from their mother, their littermates, their environment and their food.
Moving to a new home is a big change. New food, new water, new routines and a lot of new experiences can all upset a young puppy's tummy. That's why loose stools in the first few days at home are so common. Keep the breeder's food for the first couple of weeks, then change slowly if you need to. Read your puppy's first 24 hours at home.
How gut problems can affect behaviour
A dog with an uncomfortable tummy is often a less settled dog. The changes can be small. You might notice some of these:
restlessness, pacing or trouble settling at night
irritability, especially when touched around the tummy
more barking, reactivity or startling
trouble focusing in training
licking floors, carpets or surfaces
eating grass urgently
These signs don't always mean the gut is the cause. They're a reason to look at the whole picture, including health, sleep and stress. Read pain and aggression in dogs.
Stress affects the gut too
The link works both ways. Stress changes how the gut moves, how it absorbs food and which bacteria thrive. That's why many dogs get an upset tummy after kennels, a house move or fireworks.
So helping your dog feel calm and safe is good for their gut, and a healthier gut can help them feel calmer. Read dog decompression.
How to support your dog's gut health
Small, steady habits make the biggest difference. You don't need expensive extras. These are good places to start:
feed a consistent, good quality diet that suits your dog
change food gradually over 7 to 10 days
keep treats simple and not too rich
make sure fresh water is always available
protect sleep and keep daily routines predictable
reduce stress with calm enrichment and decompression time
ask your vet before adding probiotics or supplements
When to see your vet
Speak to your vet if your dog has diarrhoea for more than a day or two, blood in their stool, vomiting, weight loss, a poor appetite or a sudden behaviour change. Ongoing tummy problems are worth checking properly, as they can have many causes.
RENEE'S TIP
Keep a two-week log of meals, treats, stools and behaviour. Note any loose stools, wind or unsettled evenings alongside what your dog ate that day. Patterns often show up quickly, and your vet will find it really helpful.
QUICK CHECK
ā The gut and brain talk to each other through the gut-brain axis
ā An upset gut can make dogs restless, irritable and less focused
ā New puppies often get loose stools from all the changes
ā Change food slowly and keep routines predictable
ā See your vet for ongoing tummy problems or behaviour changes
ONE-TO-ONE HELP
Help with an unsettled dog
If your dog struggles to settle and your vet has checked their health, I can help you build calm routines in an online Dog Behaviour Consultation from wherever you are.
Online on Teams, wherever you are. 30 or 60 minutes.
FAQs
Can gut health affect a dog's behaviour?
Yes. An uncomfortable gut can make dogs restless, irritable and less able to cope with stress.
What is the gut-brain axis in dogs?
The two-way communication between the gut and the brain, through nerves, hormones and the immune system.
Why does my new puppy have a loose stool?
New food, water, routines and stress can all upset a puppy's tummy. Keep their usual food and speak to your vet if it lasts.
Should I give my dog probiotics?
Ask your vet first. Some dogs benefit, but the right choice depends on your dog's health and diet.
What are signs of gut problems in dogs?
Loose stools, wind, tummy gurgles, grass eating, licking surfaces and changes in appetite.
ABOUT THE AUTHOR
Renee Patience Ā· National Dog Trainer of the Year 2025
Founder and head trainer of Paws Academy, with more than 30 years training dogs and a Level 6 Diploma in Applied Canine Behaviour. Renee has competed in agility, obedience and heelwork to music across the UK, including at Crufts and Olympia, has appeared on CBBC, and is the author of the Modern Training Guides and the Modern Breed Handbook series. Pictured with her boxer, Kookie.
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