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Background: Mares are the only companion animals simulating women in the large diameter of their follicles. Horses start reproduction at the age of three years, and some of them live for >30 years, so aging influences their reproductive capacity. Mares are sensitive to summer heat stress as they can sweat like humans. Aim: The current work aimed to study the effects of age (young versus senile), season (cold versus hot), and the hormonal treatments during embryo collection on the dominant and subordinate follicular dynamics and hemodynamics and circulating ovarian hormones in embryo donor mares ovulated twice spontaneously before inducing ovulation for flushing embryos. Methods: Spontaneous oestrous cycles were studied for young mares (<10 years; N = 6) or senile (>20 years; N = 5) during months of the cold season (November to April) and hot season (May to August). In young embryo donor mares, oestrous cycles after inducing ovulation and luteolysis were studied using Doppler ultrasound. Estradiol (E2), progesterone (P4), nitric oxide (NO), total cholesterol, and lactate dehydrogenase (LDH) were measured in blood serum. Results: A decrease in the dominant follicle antrum diameter (p > 0.05) and LDH (p = 0.016) was observed after inducing luteolysis in young embryo donor mares. Both human chorionic gonadotropin (hCG) and PGF2a treatments increased dominant follicle area (p = 0.0001), antrum area (p = 0.001), perimeter (p = 0.001), granulosa area (p = 0.0001), cholesterol (p = 0.0001), NO (p = 0.0001), and E2 (p = 0.0001). The dominant follicle area, antrum area, perimeter, color area, granulosa area, LDH, cholesterol, NO, and E2 increased (p = 0.0001) during the oestrous cycles of the hot season, but the circulatory % (p = 0.0001) declined. Senile mares had lower dominant follicle area (p = 0.002), antrum area (p = 0.0001), granulosa area (p > 0.05), LDH (p = 0.001), cholesterol (p = 0.0001), NO (p = 0.0001), and E2 (p = 0.0001) but higher circulatory % (p = 0.0001) and color area % (p = 0.023). The dominant follicle possesses the largest diameter, area, perimeter, granulosa area, and color area but the lowest circulatory % during spontaneous oestrous cycles, after inducing ovulation, or luteolysis with significant effects of the day of the spontaneous oestrous cycles on their dynamics and hemodynamics. Conclusion: During hot months, mares treated with hCG ovulated 24 hours later and prostaglandin-induced luteolysis was followed by new ovulation five days later. Follicles ovulated during the hot months were larger than those ovulated during the cold months and both had nearly the same color area %. Senile mares ovulated follicles with a lower area and antrum area but a higher color area %, so senile mares can be used as embryo or oocyte donors during the hot season. [ABSTRACT FROM AUTHOR]

The present study aimed to compare the reproductive outcomes after the blind application of the standard Ovsynch and Presynch Ovsynch protocols on Egyptian Buffaloes (Bubalus bubalis) during the breeding season. Fifty multiparous Egyptian buffalo cows of an unknown stage of the estrous cycle were randomly divided into two groups: 1) the standard Ovsynch protocol (first GnRH (G1) at d0, PGF2α at d7, and second GnRH; G2 56 h later and 2) the pre-synch Ovsynch (G6G-Ovsynch) protocol (PGF2α and GnRH 2 days apart 6 days before starting G1 of the standard Ovsynch). Cows were subjected to timed artificial insemination (TAI) 16 and 40 h after the G2 injection in both groups. Blood sampling and ovarian transrectal ultrasonography were performed at three time points, PGF2α, G2, and 2 days after G2. Serum progesterone (P4) (ng/mL) concentrations were significantly higher in the G6G-Ovsynch group than in the Ovsynch group at the time of PGF2α and two days after the G2 injection, but they were lower (P < 0.05) at the G2 injection. The Vascularity index of the corpus luteum (CL) and dominant follicle (DF) wall area (%) were higher (P < 0.05) in the G6G-Ovsynch group compared to the Ovsynch group. The ovulatory response indicated by the presence of CL at d7 was significantly higher in G6G-Ovsynch than in Ovsynch (73 vs. 51%, respectively). Moreover, a higher (P < 0.05) pregnancy rate was observed in G6G-Ovsynch than in the Ovsynch group. In conclusion, the blind application of the G6G-Ovsynch improved the ovulatory response in the early stages of the synchronization protocol and raised the pregnancy rates in Egyptian buffaloes. [ABSTRACT FROM AUTHOR]

Melatonin is known to protect sperm against freezing‐inflicted damage in different domestic species. The aim of the study was to evaluate the effect of supplementation of semen extender with melatonin on the quality and DNA integrity of cooled and frozen/thawed rabbit spermatozoa. We also investigated whether the addition of melatonin to the semen extender could improve the fertility of rabbit does artificially inseminated with frozen/thawed semen. Semen samples collected from eight rabbit bucks were pooled and then diluted in INRA‐82 supplemented either with (0.5, 1.0 or 1.5 mM) or without (0.0 mM) melatonin. Diluted semen was cooled at 5°C for 24 hr. For cryopreservation and based on the first experiment's best result, semen samples were diluted in INRA‐82 in the presence or absence of 1.0 mM melatonin and then frozen in 0.25 ml straws. Following cooling or thawing, sperm quality and DNA integrity were evaluated. Furthermore, the fertility of frozen/thawed semen was investigated after artificial insemination. Supplementation of semen extender with 1.0 mM melatonin improved (p <.05) motility, viability, membrane and acrosome integrities in cooled semen compared with other groups. Sperm quality and DNA integrity were higher (p <.05) in frozen/thawed semen diluted in 1.0 mM melatonin‐supplemented extender than in the control group. Conception and birth rates were higher in does inseminated with 1.0 mM melatonin treated semen compared with the controls. In conclusion, supplementation of semen extender with 1.0 mM melatonin improved the quality of cooled and frozen/thawed rabbit spermatozoa. Melatonin can preserve DNA integrity and enhance the fertility of frozen/thawed rabbit spermatozoa. [ABSTRACT FROM AUTHOR]