The effect of month and breed on plasma adrenocorticotropic hormone concentrations in equids.

This study investigates how the time of year and breed of equine might influence levels of plasma adrenocorticotropic hormone (ACTH), which is critical for diagnosing PPID, a common hormonal disease in horses and ponies. The research uncovers significant patterns and differences in ACTH concentration across different equine breeds and during various months.

Objectives of the Study

• This study aimed to understand how breed and time of the year influence the concentrations of plasma adrenocorticotropic hormone (ACTH) within equids — family of animals including horses, donkeys, and ponies.
• Another objective was to establish whether these factors might pose potential challenges when using ACTH concentrations for diagnosing Pituitary Pars Intermedia Dysfunction (PPID) — a common disease in equids — by elevating ACTH levels.

Methodology

• Ten breeds of equine were selected for the study. The breeds chosen include Arabians, Cobs, Connemara ponies, donkeys, Irish Sports horses, New Forest ponies, Shetland ponies, Thoroughbreds, Warmbloods, and Welsh breeds.
• A detailed laboratory dataset containing information about plasma ACTH concentrations was utilized to examine the breed’s role and the time of year on ACTH levels.
• By undertaking a multivariable analysis, the researchers were able to evaluate the influence of month and breed on plasma ACTH concentrations.

Findings of the Study

• The study found a clear circannual pattern (occurring yearly) in the concentration of ACTH, with the lowest levels (nadir) detected in April and the highest levels (peak) seen in September.
• Among the breeds examined, Arabian horses and donkeys displayed higher ACTH concentrations than other breeds, predominantly between May and November.
• In contrast, Shetland ponies, as well as Welsh breeds, exhibited relatively higher ACTH concentrations only between July and November.
• The study found that the annual rise in plasma ACTH levels started to occur at the end of April or the start of May, a time characterized by increased daylight. The levels then decreased after late September when the length of the day fell below 12 hours.
• Substantial differences in plasma ACTH between breeds were noticed, suggesting that both breed and time of the year influence ACTH concentrations and should be considered when interpreting plasma ACTH concentrations in equids suspected of having PPID.

Implications of the Findings

• Understanding these variations is critical for recognizing and interpreting the health of equids accurately.
• It is particularly significant for equid breeders, veterinarians, and scientists who study or manage PPID and need to understand these factors to make accurate diagnoses and treatment decisions.