In Vitro Investigation of Equine Gut Microbiota Alterations during Hypoglycin A Exposure

Hypoglycin A is a plant-derived protoxin that causes atypical myopathy in equids. Its toxic metabolites have been well characterised, but the potential contribution of the gut microbiota in its transformation remains unresolved. In atypical myopa-thy-affected-horses, metabolomic and microbiome studies have reported alterations in metabolic markers and faecal microbiota composition, pointing to a potential disruption of microbial homeostasis. However, in vivo observations are strongly confounded by host-related factors, underscoring the need for controlled in vitro approaches. To address this, we used a static batch fermentation model simulating the equine colon to investigate the direct effects of hypoglycin A on microbiota composition and activity. Faecal inocula from healthy horses were incubated in control and hypoglycin A-treated fermenters for 48 h, with serial analyses of hypoglycin A concentration, short-chain fatty acids, and 16S rRNA gene profiles. Results showed significant microbial-associated hypoglycin A degradation without evidence of toxic metabolite formation. Analysis of α- and β-diversity revealed effects of both incubation time and hypoglycin A exposure, with specific taxa such as Paraclostridium affected. This study provides the first in vitro evidence that the equine microbiota contributes to hypoglycin A degradation.