No Gut, No Horse? Why gut bugs are essential for optimum health and behaviour

The UK association World Horse Welfare organized a webinar on this subject. Below are my transcript notes, if you don’t have time to watch the entire webinar.

« We welcomed veterinarian Dr. Amber Batson to talk to us about how our horses’ gut health plays a significant role in their overall health and welfare. Amber guided us through the known links between gut health and behaviour and explain what we need to know as owners to optimise gut health in our horses. Jo Hockenhull, animal behaviour and welfare research scientist and EBTA member, joined Amber on the panel to answer questions on the night about the equine gut biome and how this may affect your horse’s health and behaviour. 

Dr Amber Bateson “Understand animals” provide behaviour education

Horses : one of the best converters from plant to calories. Gut bugs responsible for this (short chain fatty acids)

Gut bugs are everything, they provide calories ,nutrition, but also health and behavior

Gut break down food , make vitamins, make chemicals that affect gut tissue activity, they affect brain activity. She refers to bugs as “chefs” , they combine ingredients given, create different products, they can absorb into blood stream ,and affect other parts of the body. They stimulate and influence the immune system. White blood cells are produced by bone marrow, white blood cells are also involved in inflammatory responses. This processes are switched on and off by the gut.

Activation of this tissue (gut) impacts what happens in bone marrow reg. immune response.

Guts also impact promotion of fat storage.

Gut bugs also impact nerve growth and bone density. Also have impact on medication. Impact on pain perception as well.

Tryptophan is precursor to serotonin. Serotonin is essential to gut motility. Serotonin might be solely responsible for gut motility.

A lot of serotonine is found in brain and elsewhere. Gut serotonin cannot get into the brain. 90% of serotonin influences the brain. How? Some of tryptophan is left alone by gut bugs, gets in the brain, crosses the brain blood barrier and gets into the brain. Acts as anti anxiety, anti aggression, plays role in mood, sleep. 

Tryptophan can be made into serotonin, but also indoles, kynurenine. 

We need tryptophan to be converted in outcomes in right outcomes. If we have too much indoles reg. to serotonin, we have a bad immune reaction and impact on sleep , mood. 

Just increasing starch content in diet increased vigilance (24:30), worrying about new stimuli that are coming in the environment. Behaviour changes because of changes in diet

Can lead to depression in some instances; gut bugs have impact on learning capacity.

Make it much harder to make memories. The less you have gut bugs available, and the less diverse they are in your gut , more difficult to form memory (and thus impact learning)

How do the get bugs get there? Some crossing from mum into the placenta into fetus. But most during birth. Vagina of mum contains a lot of bug, that is the initial colonization. Colostrum is rife with bacteria and other bugs.

We don’t let them mutually groom, we don’t let them sniff their horses and roll on the ground : leading to impoverished (microbiota). Diet , antibiotic exposure and hygiene are likely factors (see research by Ang, 2022)

What keeps microbiota happy?

– right food (high fibre, low sugar, low starch diet)

– movement is really important (horses evolved to eat and move, Williams 2011, 2015. Gut motility on pasture vs stabled horse. Significant reduction of gut motility when horse stable. Colic risk increased in stabled horses) horses need to move all the time. 

-Low stress ‘(sources of stress include pain, ill health, fear , being unable to  assess and respond to potential threats, social isolation, lack of positive bonds, frustration caused by barriers, transportation, environmental changes)

-short fast activities: when horse is running it is diverting blood from gut to muscles. horses are not endurance runners

-sleep: horses need approx.. 4hours sleep across 24h, gained best when in positive social company, on comfortable surfaces, in open spaces, not in pain.)

see Theelan research 2021

Guts: at the heart of disease? Hippocrates

Probiotic supplements do not seem to be the solution? Prebiotics (feeding bugs) etc? maybe.


  • meeting emotional needs
  • right ingredients for cooks = gut bugs: high fibre, low sugar, low starch, trickle fed (spread over the day vs 3 meal approach), diets containing plant variety and access to soil, is the best source
  • multi modal approach

Question & Answer to panellists below references, scroll down


Jo Hockenhull: Animal behaviour and welfare research scientist at Bristol veterinary school

How to support gut bugs if grazing is prevented. Eg laminitis etc. getting on top of pain is important. If not they have stress: impact on gut bugs.

Companionship, ways of providing social contact. Provide smell of companion. 

Ways to make companionship better. Movement is better. Many mini stations rather than 1.

EMS / laminitis : straw is getting more attention. (as solution, to reduce nutritional load in cases of laminitis/EMS?)

Obesity: is inflammation. If we shift tryptophan serotonin levels in gut we further obesity.

Thinking weight loss in horses is not just bringing them off the grass. We need to think companionship / activity etc. address behavioural needs simultaneously, if not we might not be able to help.

High level of cortisol : damages gut bugs

Equine dental care : essential. High fibre diet is important also for dentition of horses (1:00)

How to measure gut health /gut bugs

Maybe we don’t have to measure it but we should keep horses stress level low.

There are tests available. we don’t know enough about that now.

What is common in domestic horses does not mean it is normal. What is ideal population of gut bug: we need more research on free range horses (vs domesticated, who were subject to antibiotics, early weaning etc.)

What bugs are making is more important (than what the microbiota is made of); this is what we need to measure. 

Minimize antibiotics. We have no evidence that probiotics get to the right place in the gut.

Careful worming. Faecal assessment to assess what they need.

Gradual changes through seasonality in gut bugs: soil changes through seasons, horse is migratory animal. 

Ant parasitic med seem to impact horses: So need to strategic worming. Just one wormer every year or every month. So with faecal account, saliva tests etc. if horse got a good immune system they are quite tolerant of those worms; they ‘ve evolved to exist with those worms. So let’s make sure we use the test appropriately and make the right decisions.

How long does it take for the gut microbiota to change to healthier biome?

biota comparison: stabled versus pasture.

When moved to pasture: have same gut population in 4 days when moved from stable to pasture.

But fungus, virus might take weeks to adjust. So we are looking at some weeks but not months to adjust.

Long term stress can cause a lot of long term issues for horses.

Stress impacts gut bugs, leaky gut (tight junctions don’t function any more). also impact on hippocampus, memory and limbic system emotion regulation. 

If horse perceives everything as threatening, switches on stress reaction.

Some horses will struggle to recover from stress.

Slightly different diets change population. High fibre low starch low sugar is definitely better.

Pun “horses for causes”

Can eating poop can be a sign of bad gut? (1:23)

Younger foals do it. After 6-8month we don’t assume coprophagia, in adult horse we don’t assume coprohagia

it might be some self-faecal-matter-transplantation. Supplement their diet to have their own gut bugs. There is some sort of imbalance but is it at the fibre level? At the gut bug level?

Final words

Many things that can be done to address the “friends forage freedom” (basic behaviour needs)

Stress reduction very important: meeting their needs. The way they are trained, handled, what they are exposed them. Make sure that how we handle them is empathic, compassionate, that their emotional needs are met

Recommended book

More resources 

– How should I feed a horse? –…

Amber’s facebook page –…

EBTA Website –

EBTA Facebook Page –… New research study reports on the use of alternative grazing systems such as tracks, equicentral and rewilding in the UK –…

Partager :