The effects of acute strenuous exercise on the faecal microbiota in Standardbred racehorses

While exercise has been found to change the faecal microbiome (FM) in laboratory animals exposed over weeks, no studies have identified immediate changes in the FM associated with short spans of intense exercise, 5 min. The purpose of this study was to test the hypothesis that acute intense exercise would alter the FM in horses. Each horse performed two rounds of testing undergoing both a graded exercise test (GXT) and a parallel standing control (SC) trial before (GXT1 and SC1) and after (GXT2 and SC2) 12 weeks of exercise training. Rectal faecal samples were taken 24 h before and after testing. Bacterial community analysis was done by sequencing the 16s rRNA (V3-V4) region via Illumina Miseq. The relative abundance of the genus Clostridium significantly decreased in SC1 (P<0.05), with a concurrent decrease in the Shannon diversity index at the species level (P<0.05). At both the genus and species levels the principle coordinate analysis (PCoA) showed significant separation when the samples collected before SC1 were compared to those collected after SC1 (P<0.05). Interestingly, we found that Fusicatenibacter saccharivorans, a bacteria found to be decreased in ulcerative colitis patients, and Treponema zioleckii, a bacteria found to degrade fructan in sheep rumen, were significantly decreased when the samples collected before SC1 were compared to those collected after SC1 (P<0.05). None of the changes observed in SC1 happened in SC2 (P>0.05). Our results indicate that very intense acute exercise does not alter the faecal microbiome of the Standardbred race horse and that 12 weeks of exercise training does not alter that response.