Gastro-Intestinal Microbiota in Equines and Its Role in Health and Disease: The Black Box Opens

Abstract

Horses are large non-ruminant herbivores and rely on microbial fermentation for energy, with more than half of their maintenance energy requirement coming from microbial fermentation occurring in their enlarged caecum and colon. To achieve that, the gastro-intestinal tract (GIT) of horses harbors a broad range of various microorganisms, differing in each GIT segment, which are essential for efficient utilization of feed, especially to use nutrients that are not or little degraded by endogenous enzymes. In addition, like in other animal species, the GIT microbiota is in permanent interplay with the host’s cells and is involved in a lot of functions among which inflammation, immune homeostasis, and energy metabolism. As for other animals and humans, the horse gut microbiome is sensitive to diet, especially consumption of starch, fiber, and fat. Age, breeds, stress during competitions, transportation, and exercise may also impact the microbiome. Because of its size and its complexity, the equine GIT microbiota is prone to perturbations caused by external or internal stressors that may result in digestive diseases like gastric ulcer, diarrhea, colic, or colitis, and that are thought to be linked with systemic diseases like laminitis, equine metabolic syndrome or obesity. Thus, in this review we aim at understanding the common core microbiome -in terms of structure and function- in each segment of the GIT, as well as identifying potential microbial biomarkers of health or disease which are crucial to anticipate putative perturbations, optimize global practices and develop adapted nutritional strategies and personalized nutrition.

Current Understanding of Equine Gut Dysbiosis and Microbiota Manipulation Techniques: Comparison with Current Knowledge in Other Species

“…were strongly associated with diarrhea [96]. The association between Proteobacteria and dysbiosis has also been demonstrated in other species [113][114][115][116]. The Firmicutes-Bacteroidetes ratio is often presented in microbiota studies and is sometimes used as a marker for dysbiosis in human medicine.…”

Dysbiosis not observed in Canadian horses with free fecal liquid (FFL) using 16S rRNA sequencing

“…While the exact causes of FFL are unknown, several factors including social stress 1 , 2 endoparasitic infection, poor dentition, and diet have been suggested as at least being contributing factors 5 . Diet 6 , environmental conditions 6 , 7 and stress 4 , 6 , 8 also have a significant impact on the composition of the microbial population (microbiota) within the intestines. An imbalance in equine gut microbiota composition (dysbiosis) is already well documented to affect the normal health and function of the gastrointestinal tract and is associated with diseases like colic 9 , colitis 10 , laminitis 11 , 12 , and diarrhea in foals 13 , 14 .…”

Exploring the Influence of Growth-Associated Host Genetics on the Initial Gut Microbiota in Horses

“…The commensal gut microbiome of horses is crucial for optimal feed efficiency, including nutrient use, inflammation regulation, immune homeostasis, and energy metabolism, to support growth [15]. In horses, the rapid growth period, similar to the infantile growth phase in humans, lasts from birth to weaning and typically occurs at 4-6 months of age [16].…”