How Does Gut Health Affect Your Horse’s Weight?

HORSEHage Feeding for Condition over Winter

How Does Gut Health Affect Your Horse’s Weight?

How does gut health affect your horse’s weight? Gut health can have a huge impact on your horse’s weight and their ability to gain, lose and maintain muscle and fat. Therefore, microbial imbalances in equine gastrointestinal (GI) tract can also have a massive impact on horse’s ability to perform and develop. But how do we know if their is a problem with our horse’s GI microbiome and what can we do to fix it?

The Equine GI Microbiome

The equine GI microbiome is the heart of gut health! A diverse community of microorganisms, inhabiting the digestive tract, the microbiome is responsible fore breaking down nearly all feed into readily available sources of energy and nutrients. For herbivores, such as horses, these communities specialise in the fermentation of fibre, providing the body with its main source of energy in the form of volatile fatty acids (VFA’s).

How Does The GI Microbiome Affect Weight?

Although management practices can affect horse weight, the GI microbiome can affect the break down and utilisation of energy ingested by the horse, and therefore their weight too.

In humans, it has been found that those with low GI microbial levels had higher fat levels, increase insulin resistance abnd greater levels of fat circulating in their blood. Meanwhile in horses, it has been found that those who are obese have different levels and variations of bacteria in their hind-gut as well.


One study found that obese horses’ gut microbiomes were enriched in 6 triglyceride (a type of fat found in the blood) associated bacterial types, while the lean horse group had no weight associations with the bacterial type. In addition, bacterial types associated with human obesity were also associated with the obese equines in the study. It is still unclear whether these bacteria are diet or genetically influenced.

On the other hand, horses with poor microbial diversity will struggle to breakdown nutrients, leading to weight loss, nutrient deficiencies and poor muscle development.


Equine Gastrointestinal Microbiome - EquiBiome Test Kit

How Can I Help My Horse’s GI Microbiome For Weight Management?

Figuring out whether there is an imbalance in your horse’s GI microbiome is the first step!

Utilising tools such as EquiBiome test kit, which is sent off for analysis, is an easy way to see if your horse’s gut flora is balanced. Not only could this identify whether an imbalance could possibly be causing weight disturbances, it will also help rule causes and symptoms of nutrient deficiencies, despite a seemingly balanced diet.

Case Study

Isobel is the owner of Tigress; a 10-year-old TB X ID mare that was home bred and now stands at 16hh. Tigress is more Thoroughbred than Irish Draft and can be highly strung and hypersensitive.

The summer before last Isobel noticed that Tigress had put on more weight than usual and was looking bloated. Her routine was to graze overnight for around eight hours to avoid the flies and then spend the day in a barn with some hay. She had never struggled with her weight before and often went off her food if she was stressed, so Isobel was quite surprised with this sudden change as she is not the type of horse that will stuff herself with grass. Isobel put the weight gain down to the fact she wasn’t in work and the grass was good.

The following summer, after just two days of being back out on grass Tigress was bloating again. Tigress’ faecal sample was sent off to the lab in July and her bloating became more pronounced and she was progressively more stressed.


Equine Gastrointestinal Microbiome - EquiBiome Case Study
EquiBiome Case Study; Isobel and Tigress

The EquiBiome test results came back in September and revealed a worryingly low diversity in the hind gut of just 630 (the average healthy horse has around 1000-1500 different species). Tigress also had high levels of certain ‘bad bacteria’, so the EquiBiome Report made several recommendations to re-balance the gut and increase the diversity.

Tigress was put on Biome Food 5 and then no.4. After five weeks Isobel noticed that the bloating had gone and Tigress then went on to spend winter in the barn with access to hawthorn, willow and over things that EquiBiome recommended alongside the Biome Food. In general she seemed more settled and Isobel was able to hack her out with less spooky behaviour.

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Le Chatelier E.,  et al. (2013) Richness of human gut microbiome correlates with metabolic markers. Nature

Morrison, P. et al (2020) The equine gastrointestinal microbiome: impacts of weight-loss. BMC Veterinary Research.

Biddle, A., et al., (2018) Microbiome and Blood Analyte Differences Point to Community and Metabolic Signatures in Lean and Obese Horses. Frontiers in Veterinary Science.

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