Faecal parameters as biomarkers of the equine hindgut microbial ecosystem under dietary change.

This research studied if measuring changes in the bacteria and other microorganisms in horse faeces can give an accurate representation of similar changes in their digestive system, specifically the caecum and right ventral colon. The study was conducted on horses whose diets were changed from high fibre to high starch, and suggests that faecal samples can indeed serve as indicators of the horse’s gut health under dietary changes.

Research design and methodology

• The research involved six horses, each equipped with a fistula (a tube-like device for access) in the caecum and right ventral colon. The horses were subjected to a dietary modification from 100% hay, which is high in fibre, to a combination of 57% hay and 43% barley, richer in starch.
• Both diets provided the same amount of energy and the transition took place over a period of 3 weeks. Digesta (partially digested food) samples from the caecum, right ventral colon, and faeces were collected twice, on the 10th and 20th days of the trial, for each horse.
• Microbial ecosystem parameters in collected samples were then assessed using classical culture techniques and biochemical methods.

Key findings

• A shift from a high fibre to high starch diet resulted in changes in bacterial composition and microbial activity in the horse’s hindgut. Identical changes were observed in the faecal microbial ecosystem, suggesting faecal samples as suitable indicators of dietary changes on the gut microbiome.
• Introduction of the high-starch diet led to higher concentrations of lipopolysaccharides, molecules deriving from bacterial outer membranes, in the faeces. This could potentially serve as a warning signal for certain health issues.
• Significant correlations were observed between the concentrations of certain functional bacterial groups (cellulolytics, amylolytics, and lactate utilizers) in the caecum and faeces, and between the colon and faeces. This further supports the notion that faecal samples can represent changes in the microbial ecosystem of the proximal hindgut.
• Principal component analysis, a statistical technique used to understand patterns in data, revealed strong correlations between certain parameters in the caecal/faecal and colonic/faecal samples. Among these were total anaerobic and cellulolytic bacteria concentrations, as well as valerate, L-lactate and lipopolysaccharide concentrations. This provides additional evidence supportive of the research hypothesis.

Implication of the findings

• The results point towards an easier, non-invasive way of assessing changes in the equine gut microbiome as a result of dietary changes. Instead of needing direct access to the caecum and right ventral colon, one can analyse faecal samples for an accurate representation.
• The findings could contribute to ongoing efforts to bolster understanding of equine gut health and its relationship to disease. It could offer veterinarians and horse caretakers critical insights that help inform more precise dietary strategies and interventions for managing gut health.