Investigation of breed differences in plasma adrenocorticotropic hormone concentrations among healthy horses and ponies.

This research investigates how the levels of a specific hormone called adrenocorticotropic (ACTH) vary across different horse breeds during different seasons. The study found that ACTH levels differed significantly among different breeds in the autumn, but not in the spring, suggesting that breed-specific considerations are important when interpreting these hormone levels in horses.

Background of the Study

• ACTH is a hormone often measured in horses to diagnose pituitary pars intermedia dysfunction (PPID), a common endocrine disorder.
• The concentration of this hormone can be influenced by several factors, including the breed of the horse. Hence, the study aims to evaluate breed-based differences in plasma ACTH concentrations among healthy horses and ponies.

Methodology

• The study included Thoroughbred horses, Shetland ponies, and non-Shetland pony breeds. The animals included in the study showed no signs of illness, lameness, or clinical signs of PPID.
• Blood samples were collected twice, once around the autumn equinox and once around the spring equinox. The ACTH concentrations in these samples were then measured using a chemiluminescent immunoassay, a biochemical test used to detect the presence of the hormone.
• Statistical analyses were performed to compare ACTH levels between breeds in both seasons. Reference intervals for ACTH concentrations for each breed group per season were also calculated.

Findings

• In autumn, non-Shetland pony breeds and Shetland ponies had higher ACTH concentrations compared to Thoroughbred horses. Further, Shetland ponies had higher ACTH concentrations than non-Shetland pony breeds. However, no such differences were observed in the spring.
• The upper limits for ACTH concentrations in autumn were significantly different between Thoroughbreds and pony breeds.

Conclusion

• The study highlights that while determining and interpreting ACTH concentrations in horses and ponies, the breed of the animal and the season of testing should be considered.