Supplementary figure 1: Denaturing gradient gel electrophoresis of the PCR amplified V2/V3 region of 16S rRNA genes from the caecal fluid of horse 1. The left and right gels were loaded with 1 and 6 l of PCR product respectively. Numbers at the top of the gel indicate time, in hours post-oligofructose administration (POA), and 5 L = ladder. Horse 1 initially exhibited histological evidence of laminitis at 12 h POA and clinical signs of laminitis at 28 h POA. Supplementary figure 2: Denaturing gradient gel electrophoresis of the PCR amplified V2/V3 region of 16S rRNA genes from the caecal fluid of horse 2. The left 10 and right gels were loaded with 1 and 6 l of PCR product respectively. Numbers at the top of the gel indicate time, in hours post-oligofructose administration (POA), and L = ladder. Horse 1 initially exhibited histological evidence of laminitis at 30 h POA and clinical signs of laminitis at 38 h POA. 15 Supplementary figure 3: Denaturing gradient gel electrophoresis of the PCR amplified V2/V3 region of 16S rRNA genes from the caecal fluid of horse 1. The left and right gels were loaded with 1 and 6 l of PCR product respectively. Numbers at the top of the gel indicate time, in hours post-oligofructose administration (POA), and L = ladder. Horse 1 initially exhibited histological evidence of laminitis at 30 h POA 20 and clinical signs of laminitis at 43 h POA. Supplementary figure 4: Denaturing gradient gel electrophoresis of the PCR amplified V2/V3 region of 16S rRNA genes from the caecal fluid of horse 1. The left and right gels were loaded with 1 and 6 l of PCR product respectively. Numbers at 25 the top of the gel indicate time, in hours post-oligofructose administration (POA), and L = ladder. Horse 1 initially exhibited histological evidence of laminitis at 12 h POA and clinical signs of laminitis at 20 h POA. Supplementary figure 5: Denaturing gradient gel electrophoresis of the PCR 30 amplified V2/V3 region of 16S rRNA genes from the caecal fluid of horse 1. The left and right gels were loaded with 1 and 6 l of PCR product respectively. Numbers at the top of the gel indicate time, in hours post-oligofructose administration (POA), and L = ladder. Horse 1 initially exhibited histological evidence of laminitis at 18 h POA and clinical signs of laminitis at 26 h POA. 35 Supplementary table 1: Raw qPCR and FISH data presented in this publication. FISH data are expressed as relative abundances, expressed as a percentage of the total EUBMIX-hybridising organisms. Subjective scores were: 0%, occasional presence (fewer than one microorganism per field of vision and not possible to quantify), <1%, 40 1-5%, 6-10%, and then in 10% increments up to 91-100%.