Abstract
The purpose of the present study was to compare digestibility of grass hay, faecal and plasma volatile fatty acid (VFA) concentrations, and faecal bacterial abundance in overweight and moderate-condition mares. Five overweight adult mixed-breed mares and five adult mixed-breed mares in moderate condition were housed individually and limit-fed orchard grass (Dactylis glomerata) hay at 20g/kg body weight (as fed) daily for 14 d. Forage DM and fibre digestibility were determined using AOAC methods; digestible energy was measured using bomb calorimetry; plasma and faecal VFA concentrations were determined by use of GC and MS; faecal Firmicutes, Bacteroidetes, Fibrobacter succinogenes, Ruminococcus flavefaciens and total bacteria abundance was determined by quantitative real-time PCR using previously designed phylum-specific 16S ribosomal RNA gene primers. No differences in hay digestibility, faecal VFA concentrations or faecal bacterial abundance were detected between overweight and moderate-condition mares. Mean plasma acetate concentrations were higher (P=0·03) in overweight (1·55 (range 1·43-1·65) mmol/l) v. moderate-condition (1·39 (range 1·22-1·47) mmol/l) mares. We conclude that the higher plasma acetate in overweight mares should be further investigated as a potential link between gut microbes and obesity in horses.
Highlights
The purpose of the present study was to compare digestibility of grass hay, faecal and plasma volatile fatty acid (VFA) concentrations, and faecal bacterial abundance in overweight and moderate-condition mares
Forage is high in fibre, which is not digested by mammalian enzymes due to the β-glycosidic bonds linking monosaccharide residues; fibres are digested by micro-organisms in the gastrointestinal tract, the caecum and colon, of the horse[12]
We evaluated the ratio of active, fibrolytic[56] R. flavefaciens and F. succinogenes (16S ribosomal RNA) v. the total number of fibrolytic bacterial copies (16S ribosomal DNA) abundance, providing a measurement of the proportion of actively replicating bacteria
Summary
The purpose of the present study was to compare digestibility of grass hay, faecal and plasma volatile fatty acid (VFA) concentrations, and faecal bacterial abundance in overweight and moderate-condition mares. Forage is high in fibre, which is not digested by mammalian enzymes due to the β-glycosidic bonds linking monosaccharide residues; fibres are digested by micro-organisms in the gastrointestinal tract ( known as gut microbes or gut microbiota), the caecum and colon, of the horse[12]. These gut microbes produce usable products (i.e. volatile fatty acids; VFA) from otherwise indigestible substrates. Plasma acetate may be aerobically oxidised and directly used for energy[27] or stored as TAG in adipose and skeletal tissue[28]
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