A healthy gut microbiome critical to horse health

Immune, neurological, and hormonal systems can all be affected by this microbial community

A healthy gut microbiome critical to horse health
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Although invisible to the naked eye, the horse and human cannot exist apart from the biology and ecology of their microbiome and the microbiome is being heralded as the next most important bodily system.

There is emerging evidence the gut microbiome — with its complex interactions of microbial communities including bacteria, archaea, parasites, protozoa, viruses and fungi — is involved in more than just food digestion, and that the microbiota interplays intimately with the immune, neurological, and hormonal systems of the body. Even glucose and energy metabolism have been found to be influenced by the microbiome.

Equine veterinarians and horse owners have long been aware of the notoriously sensitive nature of the horse’s digestive system. To a large degree, the horse owes this sensitivity to the ecology of the microbial community within the digestive tract. The equine microbiome is intrinsically linked to the horse’s physical, mental and emotional soundness. As such, circumstances that disturb its health and balance have numerous consequences.

Dysbiosis refers to an imbalance in the intestinal microbiota that precipitates changes in health. When this imbalance is severe in the horse, it may clinically manifest as colic, colitis, acute laminitis, and/or diarrhea. Less serious derangements to the microbiota can be responsible for weight loss, ill thrift, failure to thrive, undesirable behaviours, gastric or hindgut ulceration, inflammatory bowel diseases, periodontal disease, generalized inflammation, obesity, chronic laminitis, neurological diseases and metabolic syndromes. Because it is difficult to diagnose dysbiosis, its connections to various illness often go unrecognized.

Research has found the microbiome of non-domesticated horses includes a more diverse spectrum of microbiota, and this may explain the sensitivity of the domestic horse to gastrointestinal tract diseases in comparison to their wild counterparts.

The microbiome is entirely unique to each being. The horse is initially exposed to micro-organisms at birth as the foal passes through the birth canal and then exposure continues through nursing and exploration of the environment. The change in the population and composition of the young horse’s microbiome during the first six months of life is remarkable when considering the intestinal flora goes from sterile in utero, moves through a milk diet and then to a relatively stable and teeming microbiome capable of digesting a diet based solely upon plant fibre and forage.

Establishment of a ‘quality stock’ microbiome during a horse’s formative years is essential to a lifetime of resilient digestive health. Stall rearing, early and abrupt weaning practices, introduction of large amounts of grains and processed feeds to the young horse and social isolation are detrimental to the stability and diversity of the ‘stock’ microbiome.

Later in life, diet, stress and environmental circumstances can influence or change the microbiome as well.

The diet of the horse is likely the largest influence upon the microbiome as the diet of the horse is also the food source for the microbiome. This teeming community has a very specific, maybe even finicky appetite for quality forage.

The readily available sugars and starches, processed fats, preservatives and supplements built into designer equine rations have a profound impact upon the resident microbial populations affecting the pH and viability of the gut lining and altering the protective qualities of its mucous lining. Unnatural and unfamiliar food sources to the resident microbial populations indirectly contribute to systemic inflammation. The ongoing inflammation often triggered by today’s rich diets may actually be a contributing reason as to why health issues seem resistant to remedy. An unfavourable shift in the microbiome may potentially contribute to inflammatory conditions, insulin resistance, metabolic syndromes, allergies, poor hoof integrity and chronic laminitis.

Unfortunately, horses with smouldering dysbiosis may be perceived to be ‘just not quite right’ or ‘deficient’ in some way and synthetic solutions sought as remedies further compound the problem.

Unnatural feeding practices, stressors such as travel or changing herdmates, medications, dewormers, vaccines and steroids can all alter the delicate and at times precarious microbial balance within the hindgut. Often this results in alterations to the horse as a whole, whether it be attitude, health or performance.

Key management practices that can aid in keeping the horse’s microbiome healthy and happy include what is fed, how often feed is available, and with whom the horse eats. Plenty of high-quality long-stem fibre is the mainstay of a horse’s diet. With a variety of forages, the microbiome will be diverse, stable and resilient. Horses are trickle feeders and one could say this is a quality of the microbiome as well. Plenty of exercise and movement are favourable for gut motility and functionality.

Make changes to the diet gradually. This will allow the microbiome to adapt. Ensure plenty of fresh water is readily available as the entire digestive process ‘runs as a river.’ Horses with these management advantages are better able to maintain gastrointestinal tract normalcy, reducing chances of health and behaviour problems.

Equine husbandry must carefully consider the impact that caretaking practices have upon the microbiome because a healthy microbiome nourishes and takes care of the horse in innumerable ways. If a horse’s microbiome is happy and thriving, chances are the horse will be happy and thriving too.

About the author


Carol Shwetz is a veterinarian focusing on equine practice in Millarville, Alberta.



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