Gut microbes are essential to digestion and the wellbeing of horses and ponies. So what does the make-up of this complex microbial community tell us about the health and age of the horse?
The results of a new study paint a fascinating picture, but the work has only scratched the surface in terms of understanding the link between gut microbes and horse wellbeing.
Initial findings from the study, which followed 35 Welsh Mountain pony mares across two years, suggest that obesity in ponies may have a greater effect on gut microbes than age in healthy ponies.
Horses are known as caeco-colic fermenters, highly adapted to the ingestion (trickle feeding) of plant-based fiber diets.
Despite dietary and digestive differences, the microbial community of the equine gut has some similarities to that of humans and is dominated by bacteria from the phyla Firmicutes and Bacteroidetes.
Human obesity has been associated with reduced proportions of Bacteroidetes, and correspondingly increased abundances of Firmicutes in fecal samples.
The study team set out to evaluate whether differences in the fecal microbiome of individual horses in the study were associated with factors such as age, obesity and insulin dysregulation.
The researchers, whose findings have been reported in the journal Frontiers in Microbiology, looked at diversity – a measure of the number of different species of gut microbe, the abundance of species and the distribution or “evenness” of species within the community.
In people, a reduction in diversity has been linked to both ageing and obesity.
Dr Philippa Morrison and her colleagues examined faecal samples from obese ponies, aged ponies and healthy controls (ponies that were neither obese nor aged) which had been fed the same hay-based diet to assess differences in their gut microbes.
Surprisingly, diversity significantly increased in obese ponies (the opposite of what has been seen in obese people), and tended to increase in aged ponies (again, the opposite of what has been seen in people and similarly aged horses.)
This could mean, for example, that age-associated changes in the microbiome occur at a later actual (chronological) age in ponies than horses.
Although each group of aged, obese and normal animals could be differentiated from each other, across the whole study it was not possible to consistently predict whether ponies belonged to the aged, obese or control group by looking at differences in the faecal microbes alone.
This could be because microbes in the droppings show what is happening in only part of the digestive system. Another possible explanation is that some species of microbes are capable of performing more than one “job”, and therefore different profiles may lead to the same functional/metabolic end result. This could mean that there are several potential faecal microbial profiles that can be associated with obesity or age in ponies.
One of the research team, Clare Barfoot, a nutritionist with feed manufacturer Spillers, commented: “Although this work has only scratched the surface in terms of our understanding of the link between gut microbes, age and obesity, it’s a valuable step.
“We hope further work will give us a clearer understanding of how we can use what gut microbes tell us to positively influence the health and welfare of aged and obese horses and ponies.”
The study team comprised Morrison, Barfoot, Charles Newbold, Eleanor Jones, Hilary Worgan, Dai Grove-White, Alexandra Dugdale, Patricia Harris and Caroline Argo.
Morrison PK, Newbold CJ, Jones E, Worgan HJ, Grove-White DH, H. Dugdale AH, Barfoot C, Harris PA and Argo CM (2018) The equine gastrointestinal microbiome: Impacts of age and obesity. Front. Microbiol., 07 December 2018 https://doi.org/10.3389/fmicb.2018.03017
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