Analysis of competition stress on the microbial population in the equine hindgut.

The horse is a nonruminant herbivore where fermentation of chyme occurs in the hindgut (cecum and colon). Within this area, there is a dynamic microbial population that serve the host through immune stimulation, energy extraction, detoxification and pathogen exclusion. The impact of stress on this diverse microbial ecosystem has been seen to have an effect on the numbers of microflora that populate this area. This stress could affect health, welfare, and/or performance. Despite this, scientific literature currently provides limited details on the hindgut microflora response to stress. In particular, competition stress which is a regular experience for most performance horses. The aim of this study was to assess if the stress experienced while performing at competition had an effect on the numbers of hindgut microorganisms present within fecal samples. Fecal samples were obtained from 8 horses, aged 6 – 19 (mean = 10.38 ± 1.95), over a 5 day period. All horses participated in a showjumping competition on Day 2 of sampling. Samples were collected 3 times daily. All participants were clinically healthy and no dietary changes or medication had been given in the 2 months prior to sampling. 10-fold serial dilutions were conducted on blood agar. Total bacterial counts were enumerated. The cultured bacteria were identified to species level using biochemical tests. 14 bacteria species were identified over the 5 day sampling period. Decreases in total bacterial numbers occurred within a 24hour period post-competition in total bacterial numbers. A significant difference was identified on total bacterial numbers between baseline values of day 1 and day 5 and between day 3 and day 5 (P<0.05). No significant difference was found on total bacterial numbers between baseline values of day 1 and day 3 (P>0.05). In conclusion, competition stress had a significant impact on bacterial numbers over the 3 day period post-competition. This could suggest that prolonged exposure to competing or competition environments could have a detrimental effect on a horse’s health and performance. Further research is required to establish the impact of these microbial variations on the horse.