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