BACKGROUND: Fecal microbiota transplantation (FMT) has been used as a treatment option for horses ( METHODS: This study aimed to evaluate the impact of oxygen exposure and different protectant solutions on bacterial viability before and after freezing using horse feces. Fecal samples from 10 healthy horses were aliquoted and diluted in cryoprotectant solutions containing antioxidants ( RESULTS: Freeze-thawing decreased bacterial viability by 47% (mean ± SD: 51 ± 27% before, 27 ± 8% after
CONCLUSIONS: Fresh FMT solutions may be better for treating horses with dysbiosis, but if freezing cannot be avoided, glycerol should be used to dilute feces.