Effect of Intense Exercise on the Level of Bacteroidetes and Firmicutes Phyla in the Digestive System of Thoroughbred Racehorses.

Exercise significantly affects the body of both animals and humans, including the composition of the digestive microbiome. This study aimed to determine the changes in the composition of the most numerous bacterial phyla (Firmicutes and Bacteroidetes, as well as the level of the Lactobacillaceae family) in the digestive system of horses under the influence of physical effort. The study included a group of 17 Thoroughbred racehorses at the age of 3 years, fed the same forage, from whom feces samples were collected individually before and 48 h after physical effort. The obtained samples were subjected to DNA isolation and RT-PCR analysis. The results showed a significant increase in the level of both phyla after exercise compared to the state before physical effort; there were no such differences in the level of facultative aerobes, i.e., the Lactobacillaceae family (although a decreasing tendency was found after exercise). In addition, the analysis of the level of the studied phyla indicates individual differences in horses' response to the effort.