Endocrine and Electrolyte Balances during Periovulatory Period in Cycling Mares.
Authors: Satué Katiuska, Fazio Esterina, Muñoz Ana, Medica Pietro
Journal: Animals : an open access journal from MDPI
Summary
# Editorial Summary: Endocrine and Electrolyte Balances during the Periovulatory Period in Cycling Mares The periovulatory period in mares involves activation of the hypothalamic-pituitary-adrenal (HPA) axis, yet the precise interplay between stress hormones, aldosterone, and electrolyte regulation around ovulation remains poorly characterised. Researchers tracked daily blood samples from 23 Purebred Spanish broodmares across a 10-day window centred on ovulation (day -5 to day +5), measuring ACTH, cortisol, aldosterone, and the key electrolytes sodium, potassium, and chloride using immunoassays and ion-selective electrodes. ACTH and cortisol both peaked significantly at ovulation (day 0) before declining, with aldosterone similarly elevated at this timepoint; notably, sodium and chloride concentrations also spiked at ovulation, whilst potassium dipped on day 0 before rising again by day +1. The modest correlations observed between ACTH and cortisol (r = 0.20) and between ACTH and aldosterone (r = 0.32) suggest that whilst the pituitary-adrenocortical axis does influence steroid hormone secretion around ovulation, additional regulatory mechanisms are at play—and critically, these hormonal shifts appear mechanistically separate from the observed electrolyte patterns. For practitioners managing mares during their fertile window, these findings underscore that ovulatory stress responses involve complex endocrine signalling beyond simple HPA activation, potentially informing considerations around mare handling, supplementation strategies, and physiological demands during breeding seasons.
Read the full abstract on PubMed
Practical Takeaways
- •Understanding the natural hormonal surge at ovulation may help explain behavioral changes and physiological stress responses in mares during this critical reproductive window
- •The electrolyte shifts during periovulation are modest and unlikely to require clinical intervention in healthy cycling mares, but awareness of this pattern is useful for interpreting bloodwork around breeding time
- •For reproductive management, knowing that ACTH and cortisol elevation extends several days post-ovulation may inform timing of breeding-related procedures or stress management in broodmares
Key Findings
- •ACTH, cortisol, and aldosterone all peak at ovulation (day 0) in cycling mares, with ACTH and cortisol remaining elevated through day +3 to +5
- •Sodium and chloride concentrations are elevated at ovulation compared to day -5 and +5, while potassium is significantly lower at day 0 compared to day +1
- •Weak correlations between ACTH and cortisol (r=0.20) and between ACTH and aldosterone (r=0.32) suggest other regulatory mechanisms beyond direct pituitary control influence these hormones during the periovulatory period
- •HPA axis stimulation during periovulation appears independent of overall electrolyte pattern changes, indicating separate regulatory pathways