The Equine Hindgut Microbiome

At Phileo by Lesaffre, we offer solutions to support equines by looking at the true source of many of their problems and ailments - the hindgut microbiome. It is about more than just gut health!

More than 2,000 years ago, Hippocrates is purported to have said ‘all disease begins in the gut’. Today we are starting to understand he may have been right. Our understanding of the role of micro-organisms in shaping host health, welfare and performance are rapidly advancing. This new knowledge is already dramatically changing our understanding of how the equine hindgut microbiome can shape and determine our horse’s health, welfare and well-being.  

We now know microbial communities have a symbiotic relationship with their host, and they have a significant effect on the horse, including digestion, behaviour, homeostasis and regulating immune function. We also know that when an imbalance occurs among these microbes (known as “microbiota dysbiosis”) this can lead to a disruption of normal bodily function and, in turn, cause issues such as cancers and cardiovascular, respiratory, and neurological diseases.

Focus on the equine hindgut

The horse is a hindgut fermenter, meaning they rely heavily on digestion through the process of fermentation in the hindgut for most of their nutritional and metabolic energy requirements. The hindgut consists of the caecum and colon, and it contains trillions of micro-organisms which are the real suppliers of power, health and nutrition.

In fact, the hindgut microbiome supplies the horse with up to 70% of the total metabolic energy requirements for maintenance alone. This underlines the need to focus first on fueling the hindgut - then the stomach or small intestines - when feeding and formulating diets to ensure all nutritional and metabolic requirements are met.

The epithelial lining of the hindgut also has a critical role to play in immunity, with up to 80% of the immune function controlled by the microbiome.

The hindgut microbiome - a balancing act

In a healthy state, the trillions of microbes which dwell in the caecum and the colon live in a harmonious balance, which is fundamental to the overall health and well-being of the animal.

The hindgut microbiome is irrefutably linked to fertility, the respiratory system, cardiovascular system, development, performance, recovery, metabolic conditions and emotional well-being. Therefore, we must ensure the microbes remain in balance and the microbiome as a whole remains stable to prevent issues like hindgut dysbiosis.

When hindgut dysbiosis occurs, bacteria that produce lactic acid flourish which causes a significant drop in pH and, often, a condition known as acidosis. The epithelial lining of the hindgut becomes inflamed, negatively impacting the delicate mucosal membranes that form a protective barrier along the hindgut. These membranes are also lined with villi, which are tiny finger-like projections that are responsible for absorbing nutrients and form tight junctions to prevent the contents of the hindgut from leaking into the rest of the body.

When conditions within the hindgut deteriorate, it can quickly progress to colonic ulcers, leaky gut syndrome, colic or systemic acidosis which can be displayed as a health condition or behavioral changes seen when ridden, handled or stabled. Horses can also lose body condition, their coat can become dull, they can be “difficult” to handle or ride, and their manner can seem lackluster - potentially indicating an additional negative effect on the horse’s emotional well-being.

Effect of stressors on the microbiome

We are only just beginning to learn the true role of these microbes and their impact on our horses’ lives. However, research clearly shows that stressors in all their different forms are a key contributor to microbial changes within the hindgut. Stress actually increases the number of microbes that produce acid in the gut, causing dysbiosis. This was previously thought to be solely affected by the diet, but we now know that stress is an important contributor.

Horses and ponies experience causes of stress daily, which can include travel, stabling arrangements, medical treatments, turn-out time, feeding times, performance demands, competitions, weaning, and changes in handlers and riders, diet (including a new forage bale), exercise regimen, home or stable mate. It is impossible to remove all causes of stress in reality, but we can look carefully at how we manage these events to minimise their impact on the hindgut microbiome.

To learn more about the microbiome, visit our blog or get in touch with us directly.