Characterisation of the faecal metabolome and microbiome of Thoroughbred racehorses

Abstract

SummaryReasons for performing study: The intestinal bacterial community of the horse is a key determinant of intestinal and whole-body health. Understanding the bacterial community structure and function is an important foundation for studies of intestinal health and disease.Objectives: To describe the faecal bacterial community and the volatile organic compounds (VOCs) of the faecal metabolome of healthy Thoroughbred (Tb) racehorses, and to characterise responses to dietary supplementation with amylase-rich malt extract.Study Design: This was an intervention study performed with eight privately-owned Thoroughbred racehorses in active race training. Faecal samples were collected noninvasively before and six weeks after supplementation.Methods: Faecal metabolome was characterised using thermal desorption-gas chromatography-mass spectrometry (TD-GC-MS), with spectral analysis performed using AMDIS and compared against the NIST database. Taxonomic description of the faecal microbiota was achieved using error-corrected 454 pyrosequencing data from 16S rRNA gene amplicons. Results:The faecal metabolome of our study population was dominated by organic acids, alcohols and ketones. We identified 81 different VOCs only 28 of which were present in >50% of samples indicating functional diversity. Faecal VOC profiles differed between first and second sampling point, some VOCs being significantly reduced post-supplementation, consistent with a marked response to dietary amylase-rich malt extract. Faecal microbiota was characterised as highly diverse; samples demonstrated verifiable diversity in the range 1200-3000 operational taxonomic units (OTUs) per individual. The methods used also 3 describe high levels of infrequent, low abundance OTUs. Faecal microbial community structure was found to be different following dietary supplementation. Differences in several low-abundance bacterial taxa were detected and also some evidence of inter-horse variation in response. Conclusions:The volatile faecal metabolome of Tb racehorses is dominated by organic acids, alcohols and ketones; this study demonstrates that dietary supplementation with amylase-rich malt extract may significantly alter the profile of VOCs. The faecal microbiome is highly diverse, dominated by Firmicutes and Bacteroidetes. Small but significant changes in microbial community structure were detected following dietary supplementation.Potential relevance: This study describes the faecal metabolome and microbiome of healthy Tb racehorses against which future studies of disease and dietary intervention can be benchmarked.4

The gut microbiome of horses: current research on equine enteral microbiota and future perspectives

“…Microbiomes of non-domesticated horses (left) include a more diverse spectrum of microbiota compared to those of domesticated horses (right). Beyond age, differences in housing and pasture habits [164], composition of feeding diets [165,166], contact with humans, veterinary health care and medication seem to be among the most influencing factors for equine microbiomes [101]. Interestingly, similar observations are available for the humans, since indigenous populations seem to have a much broader spectrum of microbiota compared with industrialized countries [104]s horses, seem to be significantly enriched in case of diarrhea and colitis [25,121].…”

Intense Exercise and Aerobic Conditioning Associated with Chromium or L-Carnitine Supplementation Modified the Fecal Microbiota of Fillies

“…Other studies that characterized the core fecal bacterial microbiome of Irish Thoroughbred [28] or Thoroughbred racehorses receiving different feeding regimes or dietary supplementation with amylase-rich malt extract [29] found fluctuation in the alpha diversity (phylogenetic diversity, Shannon index and species evenness). In male elite professional rugby players, exercise and associated dietary extremes not only impact gut microbial diversity but also indicate that the relationship is complex [15].…”

Effects of transport, fasting and anaesthesia on the faecal microbiota of healthy adult horses

“…The sample size was small; however, the consistency in management of these horses was considered more important than adding more horses from different origins and with different husbandry practices. There is increasing evidence that diet has a significant effect on the microbiota of horses [29,[32][33][34], whereas temporal stability of the microbiota is high when fed the same diet [35]. Microbiota differences have been shown when horses were fed grass compared with hay [30] and when high oil, high starch and high forage diets were fed [32].…”