Metabonomic characterisation of the thoroughbred racehorse

Mammalian metabolism is known to be influenced by a number of physiological and environmental factors and the metabolic phenotype of an individual includes contributions from diet and the intestinal microbiota. Intestinal wellbeing is paramount for mammalian health and it is increasingly evident that intestinal bacteria have the ability to influence the development of an array of diseases. The horse is a hindgut fermenter- a sophisticated fermentation vat, housing a plethora of gut microbes that liberate energy from high cellulose diets. Investigating the horse will further enhance our knowledge of the symbiotic relationship between the mammalian host and its consortium of gut microbes. Plasma, urine and faecal biological matrices were explored using nuclear magnetic resonance spectroscopy to identify the dominant metabolites present in a healthy racehorse population. Multivariate statistics allowed differences in metabolic profiles to be analysed between horses and within individual horses. 106 metabolites were catalogued, providing a reference tool for ‘normal’ horse NMR data. Urine samples provided the highest percentage of gut microbial derived metabolites. 32 racehorses were subsequently longitudinally sampled to investigate sources of metabolic variation such as yard origin, exercise intensity and behavioural phenotype. Gut microbial co-metabolites; such as hippurate, quinate and p-cresol glucuronide were found to be significantly associated with a number of sources of variation. Equine oral stereotypical behaviour (EOS), abrupt dietary change and high-starch diets are risk factors for colic. Gut microbes can indirectly influence behaviour and it has been postulated that stereotypical abnormalities, such as autism and EOS could be related to changes in gut microbial composition and metabolism. Urinary quinate- a dietary and gut microbial co-metabolite was found to be significantly increased in horses that displayed crib-biting behaviour compared to matched controls. Metabolic profiles from biofluids of horses on a diet trial exploring 3 diets; a traditional high-starch racing diet; a high-fat alternative and a grass only diet highlighted significant differences in gut microbial metabolism. A grass only diet had the highest level of gut microbial co-metabolites such as hippurate in comparison to the other diets and the high-fat alternative was most similar to this ‘natural’ grass metabolome. Conversely, a high-starch diet was associated with higher faecal lactic acid levels, suggesting a shift in pH and therefore microbial environment.Open Acces

The use of SIFT-MS in profiling the faecal volatile metabolome in horses with colic: a pilot study

SIFT-MS is used for the first time in profiling the volatile organic profile in faecal headspace in two groups of horses admitted to an equine hospital, one group with acute intestinal disease (colic) affecting the large colon, plus a control group of similarly managed horses admitted for non-gastrointestinal/metabolic reasons (e.g. acute orthopaedic injury). Compounds in faecal headspace which show statistically significant concentration differences between the groups are acetone and methanol. In addition, some ions at various m/z values show significantly different ion counts between the groups. Further information may be gleaned by using multivariate statistics in evaluating the differences between the two horse groups. Principal components analysis (PCA) and orthogonal partial least squares discriminant analysis (OPLS-DA) were evaluated for reducing the dimensionality of the SIFT-MS data, and OPLS-DA was found to be best at discriminating between the groups, particularly with SIFT-MS data acquired using the H3O+ precursor ion. Analysis of these data also show the significance of ammonia as a discriminating ion. These results show that SIFT-MS may potentially be used on the headspace of horse faecal samples for detecting altered microbial fermentation associated with acute intestinal disease of the colon