Abstract
Gastrointestinal microbial communities are increasingly being implicated in host
susceptibilities to nutritional/metabolic diseases; such conditions are more prevalent
in obese and/or older horses. This controlled study evaluated associations between
host-phenotype and the fecal microbiome / metabolome. Thirty-five, Welsh Mountain
pony mares were studied across 2 years (Controls, n = 6/year, 5–15 years, Body
Condition Score (BCS) 4.5–6/9; Obese, n = 6/year, 5–15 years, BCS > 7/9; Aged,
n = 6 Year 1; n = 5 Year 2, 19 years old). Animals were individually fed the
same hay to maintenance (2% body mass as daily dry matter intake) for 2 (aged /
obese) or 4 (control), 4-week periods in a randomized study. Outset phenotype was
determined (body fat%, markers of insulin sensitivity). Feces were sampled on the final
3 days of hay feeding-periods and communities determined using Next Generation
Sequencing of amplified V1–V2 hypervariable regions of bacterial 16S rRNA. Copy
numbers for fecal bacteria, protozoa and fungi were similar across groups, whilst
bacterial diversity was increased in the obese group. Dominant bacterial phyla in all
groups were Bacteroidetes > Firmicutes > Fibrobacter. Significant differences in
the bacterial communities of feces were detected between host-phenotype groups.
Relative to controls, abundances of Proteobacteria were increased for aged animals
and Bacteroidetes, Firmicutes, and Actinobacteria were increased for obese animals.
Over 500 bacterial operational taxonomic units (OTUs) differed significantly between
host-phenotype groups. No consistent pattern of changes in discriminant OTUs
between groups were maintained across groups and between years. The core
bacterial populations contained 21 OTUs, 6.7% of recovered sequences. Distancebased
Redundancy Analyses separated fecal bacterial communities with respect to
markers of obesity and insulin dysregulation, as opposed to age. Host-phenotype
had no impact on the apparent digestibility of dietary GE or DM, fecal volatile fatty
acid concentrations or the fecal metabolome (FT-IR). The current study demonstrates
that host-phenotype has major effects on equine fecal microbial population structure. Changes were predominantly associated with the obese state, confirming an obesityassociated
impact in the absence of nutritional differences. Clear biomarkers of
animal-phenotype were not identified within either the fecal microbiome or metabolome,
suggesting functional redundancy within the gut microbiome and/or metabolome.
Original language | English |
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Article number | 3017 |
Number of pages | 13 |
Journal | Frontiers in Microbiology |
Volume | 9 |
Early online date | 7 Dec 2018 |
DOIs | |
Publication status | First published - 7 Dec 2018 |
Keywords
- Age
- Apparent digestibility
- Biomarkers
- Equine
- Fecal metabolome
- Fecal microbiome
- Insulin dysregulation
- Obesity