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Animals : an open access journal from MDPI2022; 12(9); 1203; doi: 10.3390/ani12091203

Immune Functions Alterations Due to Racing Stress in Thoroughbred Horses.

Abstract: Racehorses are constantly exposed to stress. Aiming to verify the state of blood components and cortisol alterations during their routine and after races, phagocytosis and oxidative neutrophil burst assays, serum cortisol determination, erythrocytes apoptosis evaluation, lymphoproliferation assays, and blood count tests were performed in thirty Thoroughbred racehorses, which were divided in two groups. The samples were taken right after races (moment 0 d), during rest periods (-11 d, +1 d, +3 d), and after training (-8, +2, +5). In both groups, the phagocytosis showed a decrease in percentage and intensity immediately after the race when comparing samples collected during rest or training periods. In the mean values of oxidative burst on samples collected immediately after the race, group I animals demonstrated a decrease (524.2 ± 248.9) when compared with those samples collected in other moments. No significant differences were found between the results of different moments regarding the apoptotic cells and lymphoproliferation assays. The mean values of serum cortisol levels were increased immediately after racing. There was an increase in the percentage of neutrophils found immediately after the race. It was possible to conclude that, although a transient reduction was found in the number of neutrophils, the horses' adaptive function was not affected.
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Publication Date: 2022-05-07 PubMed ID: 35565629PubMed Central: PMC9104563DOI: 10.3390/ani12091203Google Scholar: Lookup
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  • Journal Article

Summary

This research summary has been generated with artificial intelligence and may contain errors and omissions. Refer to the original study to confirm details provided. Submit correction.

This research studied the effects of stress from racing on the immune function of thoroughbreds. It found that racing results in temporary changes in the horse’s immune cells and increases in cortisol levels, but the adaptive function of the horse’s immune system appears unaffected.

Research Methodology

  • The study involved performing a variety of tests on thirty Thoroughbred racehorses. These tests were conducted with the purpose to study the state of blood components and the changes in cortisol levels during the horse’s routine, immediately after races, and during rest periods. The tests included phagocytosis, oxidative neutrophil burst assays, serum cortisol determination, erythrocytes apoptosis evaluation, lymphoproliferation assays, and blood tests.
  • The horses were divided into two groups, and samples were collected at various time points: right after races, during resting periods (-11 d, +1 d, +3 d) and after training (-8, +2, +5).

Key Findings

  • The study revealed that the percentage and intensity of phagocytosis— a process where cells engulf and destroy harmful particles— decreased immediately following a race, compared to the levels during rest or training periods. This shows a direct temporary effect of racing on the immune function of horses.
  • Similarly, a decrease was found in the oxidative burst— the immune system’s response to infection— of participating animals immediately after the race. However, unlike in phagocytosis, this decrease was only noted in one of the groups.
  • The researchers did not find significant differences in the percentage of apoptotic cells and lymphoproliferation assays between the different testing moments. This implies that these aspects of immune function were not affected by the stress of racing.
  • The serum cortisol levels in the horses increased immediately after racing which is a normal response to stress.
  • The study also noted an increase in the percentage of neutrophils— a type of immune cell— immediately after racing. However, despite this temporary increase, the adaptive function of the horses’ immune system wasn’t impacted.

Conclusion

  • This research concluded that racing does produce a stress response in horses, leading to immediate but temporary changes in several immune parameters. However, the overall adaptive function of the horses’ immune system remains unaffected, suggesting that these animals are able to handle the stress associated with racing without significant long-term harm to their immune systems’ resilience.

Cite This Article

APA
Zandoná Meleiro MC, de Carvalho HJC, Ribeiro RR, da Silva MD, Salles Gomes CM, Miglino MA, de Santis Prada IL. (2022). Immune Functions Alterations Due to Racing Stress in Thoroughbred Horses. Animals (Basel), 12(9), 1203. https://doi.org/10.3390/ani12091203

Publication

Animals : an open access journal from MDPI
ISSN: 2076-2615
NlmUniqueID: 101635614
Country: Switzerland
Language: English
Volume: 12
Issue: 9
PII: 1203

Researcher Affiliations

Zandoná Meleiro, Mônica Cristina
  • Department of Surgery, School of Veterinary Medicine and Animal Science, University of São Paulo, São Paulo 05508-270, Brazil.
de Carvalho, Hianka Jasmyne Costa
  • Department of Surgery, School of Veterinary Medicine and Animal Science, University of São Paulo, São Paulo 05508-270, Brazil.
Ribeiro, Rafaela Rodrigues
  • Department of Surgery, School of Veterinary Medicine and Animal Science, University of São Paulo, São Paulo 05508-270, Brazil.
da Silva, Mônica Duarte
  • Department of Surgery, School of Veterinary Medicine and Animal Science, University of São Paulo, São Paulo 05508-270, Brazil.
Salles Gomes, Cristina Massoco
  • Department of Surgery, School of Veterinary Medicine and Animal Science, University of São Paulo, São Paulo 05508-270, Brazil.
Miglino, Maria Angélica
  • Department of Surgery, School of Veterinary Medicine and Animal Science, University of São Paulo, São Paulo 05508-270, Brazil.
de Santis Prada, Irvênia Luiza
  • Department of Surgery, School of Veterinary Medicine and Animal Science, University of São Paulo, São Paulo 05508-270, Brazil.

Conflict of Interest Statement

The authors state no conflict of interests or ethical issues regarding the publication of this manuscript.

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Citations

This article has been cited 5 times.
  1. Uchida-Fujii E, Niwa H, Senoh M, Kato H, Kinoshita Y, Mita H, Ueno T. Clostridioides difficile infection in thoroughbred horses in Japan from 2010 to 2021. Sci Rep 2023 Aug 11;13(1):13099.
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  3. James C, Lloyd EM, Arthur PG. The Level of Thiol-Oxidised Plasma Albumin Is Elevated Following a Race in Australian Thoroughbred Horses. Vet Med Sci 2025 Jul;11(4):e70487.
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  4. Wang J, Ren W, Li Z, Ma S, Li L, Wang R, Zeng Y, Meng J, Yao X. Blood-Based Whole-Genome Methylation Analysis of Yili Horses Pre- and Post-Racing. Animals (Basel) 2025 Jan 24;15(3).
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