Stress-related cortisol and progesterone concentrations influence the success of ovulation induction in estrous cats

Queens are induced ovulators, and ovulatory success varies with hormonal status and stress. This study aimed to investigate the stress and hormone related factors influencing ovulatory success in 78 queens induced to ovulate by vaginal stimulation (VS), GnRH (50 μg gonadorelin), and human chorionic gonadotropin (hCG, 250 IU) in domestic cats. Before ovulation induction, stress scores, serum anti-Müllerian hormone (AMH) concentrations, age, body weight, and estrus day were recorded. Serum luteinizing hormone (LH), cortisol, and progesterone were determined to characterize hourly from 0 to 4 h post-induction, and estradiol and progesterone were measured once daily for six days. Ovulation was histologically confirmed and progesterone concentrations were ≥1 ng/mL were classified as ovulated. The proportion of ovulated queens differed (p < 0.05) among treatments (VS; 46.2 %, GnRH; 73.1 %, hCG; 100 %). There was a positive correlation between the stress score and both serum cortisol and progesterone concentrations. A significant difference in LH concentrations was observed between ovulated and non-ovulated queens (p < 0.05). Ovulatory response in VS and GnRH groups of queens was influenced by several physiological factors, with individuals at more advanced estrus days and those exhibiting greater estradiol and lower AMH concentrations associated with a greater likelihood of ovulation (p < 0.05), whereas increasing stress score, advancing age, elevated cortisol and progesterone concentrations were associated with reduced ovulation rates (p < 0.05). Additionally, a marked post-induction increase in estradiol concentrations in hCG-treated queens (p < 0.05). Overall, ovulatory success in queens was influenced by induction method, estrus stage, stres, estradiol and AMH concentrations. Stress-associated adrenal activation may impair LH dynamics and reduce the likelihood of ovulation, whereas hCG maintained consistent efficacy even under heightened stress conditions.