Progesterone, Estradiol-17β, Cortisol, and Hematological Profile During the Estrous Cycle of Lactating Jennies: Preliminary and Comparative Observations

The purpose of this preliminary study was to evaluate the physiological pattern of steroid hormones and hematological profile during the estrus cycle of 10 lactating Ragusano jennies over a period of 29 days. The animals were analyzed in the preovulation days (−5, −4, −3, −2, −1), at the first ovulation (day 0), during the estrous cycle, and at the second ovulation (day 0*). Plasma progesterone (P4) and estradiol-17β (E2) were measured using the chemiluminescence assays, and total cortisol concentrations were measured using EIA kits; the complete blood count was analyzed using an automated cell count. A significant effect of time over 29 days for P4 (P < .0001), E2 (P < .0001), cortisol (P = .0001), and red blood cell (P < .0001) was displayed. Significant correlations among P4 and cortisol, white blood cell (WBC), neutrophils (NEUs), and lymphocytes (LYMs) (P < .0001), and among E2 and cortisol, P4, WBC, NEU, and LYM (P < .0001) were observed. Thus, these previous considerations, in physiological health jennies, showed that cortisol concentrations were markedly modified throughout the estrous cycle, according to the consistent variations of P4 and E2. From a practical standpoint, the comparison of physiological changes of steroidal hormones, with especial emphasis for donkeys' population and breed's biodiversity preservation, suggests that the luteal period in jennies is characterized by a highly stressful time point than follicular phase. However, the trend of the cortisol concentrations in the present investigation and the positive correlation with P4 could confirm this hypothesis.