Assessment of Blood Profiles and Pain in Sport Horses Undergoing Intrarectal Ozone Therapy

ABSTRACT Background Medical ozone is used in various treatments due to its oxidising properties. Objective We aimed in this study to evaluate the impact of intrarectal ozone therapy on haematological and biochemical parameters, as well as the pain induced by the procedure in sport horses. Study design In vivo experiment with 12 Quarter Horses (3 males and 9 females) used as their own controls to assess the effects of ozone therapy. Methods Blood samples were collected before treatment (Control), 24 h after ozone therapy (24 h post‐treatment), and 7 days after the last day of ozone therapy (7 days post‐treatment). These samples were analysed for haematological and biochemical parameters. Pain assessment, clinical evaluation, and the measurement of heart rate (HR) and respiratory rate (RR) were conducted before and during ozone therapy. Results Ozone therapy significantly affected haemoglobin ( F 2,20 = 5.55; p = 0.012), mean corpuscular haemoglobin concentrations (MCHC) ( F 2,20 = 16.01; p < 0.001), and aspartate aminotransferase (AST) activity ( F 2,20 = 20.49; p < 0.001). Specifically, haemoglobin concentration decreased 24 h after ozone therapy, MCHC levels increased 7 days post‐ozone therapy, and AST activity decreased 7 days post‐ozone therapy. Blood smears taken 24 h post‐treatment revealed red blood cells with membrane deformities, which normalised by 7 days post‐treatment. None of the animals exhibited clinical symptoms, although pain scores increased, although pain scores increased (before: 4.2 ± 0.4; during: 5.3 ± 0.4; F 1,107 = 5.20; p = 0.025). The reduction in haemoglobin was likely due to oxidative damage, which stimulated the production of erythrocytes with higher haemoglobin content. Lower AST levels suggested an absence of liver damage. The increase in pain scores suggests that using lower concentrations or doses in future studies might alleviate discomfort in the animals. Main limitations The study's applicability is limited by the small sample size, particularly the number of males, yet the findings provide valuable insights. Conclusions Overall, the administration of intrarectal ozone therapy over a 7‐day period in horses was associated with favourable haematological modifications, which may suggest an enhancement in systemic tissue oxygenation.