Scientists suggest reason for horses being prone to gut upsets

The nature of the diversity in gut bacteria in horses may be behind the species' vulnerability to digestive upsets, researchers suggest.
The nature of the diversity in gut bacteria in horses may be behind the species’ vulnerability to digestive upsets, researchers suggest.

Researchers who carried out an analysis of gut bacteria in horses have found possible clues as to why the species is so susceptible to digestive upsets.

Researchers from Britain set about analyzing samples from 10 horses taken from eight gut regions – one in the lower part of the small intestine and seven in the large intestine.

While the team from Aberystwyth University, in Wales, identified a core group of bacterial species in all gut regions, there were clear differences between the various gut regions.

In particular, they found that the horse’s hind gut had core bacteria made up of many low-abundance varieties of bacteria, which they said may explain why the equine hind gut was so vulnerable to change when challenged by the likes of dietary change.

This could lead to an alteration in fermentation patterns and ultimately spark metabolic disorders such as laminitis and colic.

“Further consideration must now be given to the functional role of these bacteria in order to establish how much functional redundancy exists and which bacteria are essential to maintain normal digestive function and health,” said the researchers, whose findings were published in the open-access journal, PLoS ONE.

“By knowing what makes up the core community, comparisons can now be made to different diets and when metabolic disorders (such as Laminitis and colic) are encountered,” they said. This work had scope for identifying preventive, diagnostis and treatment options, they said.

The study team said the horse had a rich and complex microbial community within its gastrointestinal tract which played a central role in both health and disease, with much of its dietary energy coming from fermentation of fibre by microbes in the hind gut.

They said they found core bacterial families in all the eight regions analysed, but there were clear differences. Compared to the ileum – the last part of the small intestine – the large intestine showed much more bacterial diversity overall, but this diversity was marked by low abundance.

The most abundant member of the core community in the ileum was Lactobacillaceae, while Lachnospiraceae was the most abundant at the upper end of the hind gut. At the lower end of the hind gut it was Prevotellaceae.

The researchers noted that the human gut microbiota appeared to be relatively stable in composition over time, with individuals maintaining a similar microbial profile whilst on a uniform diet with no gastrointestinal upset during sudden changes in diet.

“In horses, it is apparent that the microbiome of the hind gut changes rapidly in early life from birth up until 56 days of age and even in adult animals may not be stable.”

Evidence suggested that the equine gut microbial community may not be as stable as that found in the human gut, they said.

The researchers said they had shown for the first time that a core bacterial community existed in all regions of the large intestine of healthy horses on a fibre based, grass diet.

This core community was smaller than found in the rumen of cows but, unlike most other core communities that have been identified from other gut environments, was not dominated by any particular bacterial families. It was this diversity, combined with low abundance, that may make the horses’ hindgut so prone to upset.

The researchers were Kirsty Dougal, Gabriel de la Fuente, Susan Girdwood, Eric Pinloche, and Jamie Newbold, all with the Institute of Biological Environmental and Rural Sciences at Aberystwyth University, and Patricia Harris, from the Waltham Centre for Pet Nutrition in Leicestershire.

Dougal K, de la Fuente G, Harris PA, Girdwood SE, Pinloche E, et al. (2013) Identification of a Core Bacterial Community within the Large Intestine of the Horse. PLoS ONE 8(10): e77660. doi:10.1371/journal.pone.0077660

The full study can be read here

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