The objective of this investigation was to determine the ovarian response, fertility, and prolificacy of nulliparous sheep when compared to multiparous sheep after a short-term (7 days) CIDR/eCG treatment which was administered during the non-breeding season. All the multiparous sheep, whereas only 54% of the nulliparous ewes, showed signs of estrus. However, 81.8% of the multiparous sheep and 100% of the nulliparous ewes ovulated. Fertility was also low after short-term progesterone treatments during the anestrous season in maiden sheep (30.8 vs. 72.7% in multiparous ewes). Such results indicate significant differences in the response to CIDR/eCG protocols for induction and synchronization of estrus and ovulation between nulliparous and multiparous sheep during the non-breeding season.

The aim of this study was to evaluate the effect of the month of oocyte harvesting and the temperature–humidity index on oocyte number and quality harvested from Holstein cows and heifers, oocyte developmental competence, and total embryos produced in an area of intense ambient temperature for most of the year. A total of 5064 multiparous lactating cows and 2988 nulliparous heifers were used as oocyte donors and distributed across the months of the year. Overall, total oocytes per collection did not differ (p > 0.05) between cows (16.6 ± 2.7) and heifers (15.1 ± 1.8), but oocyte developmental competence was lower (p < 0.05) in cows (21.3 ± 5.4) than heifers (25.5 ± 4.0). For cows, the total number of oocytes harvested was two-fold higher (p < 0.05) in November than in May. For heifers, the total number of oocytes harvested was highest in April (17.19 ± 0.53) and lowest in May (10.94 ± 0.32; p < 0.05). For cows, total embryos were highest in November (2.58 ± 0.42) and lowest in August (1.28 ± 0.10; p < 0.05). Thus, taken together, these results indicate that severe heat stress impaired the number and quality of oocytes harvested from donor Holstein multiparous cows and heifers, oocyte developmental competence, and total embryos produced in this area of intense ambient temperature for most of the year.

Background: Season of the year can affect the reproductive behavior in Holstein cows, altering the competition of the oocytes, reflecting a reduced production of embryos. The objective of this study was to evaluate the average of total oocytes, competition of oocytes and embryos in the in vitro production process at different season of the year in Holstein cows. Methods: During the four seasons of the year, was performed on each of the oocyte donor cows (winter, n = 957; spring, n = 1571; summer, n = 1776; autumn, n = 1128), by in vivo transvaginal follicular aspiration technique after the collection were subjected to the embryos production in vitro. Result: The highest number of total embryos were produced in winter and autumn, compared to spring and summer (3.76±0.16 and 3.54±0.18 vs. 2.73±0.11 and 2.45±0.10; respectively, P less than 0.05). During winter, a higher percentage of oocyte competition was observed, followed by autumn and spring and less competition shown in summer (26.03±0.39, 19.08±0.29, respectively, P less than 0.05). The quantity and competence of the oocytes collected and in vitro embryo production were drastically reduced during the hottest months of the year in this area of intense heat.

The aim of this study was to evaluate whether the administration of 100 IU of equine chorionic gonadotropin (eCG) or human chorionic gonadotropin (hCG) at the time of the second injection of a double prostaglandin F?? (prostaglandin PGF2?) protocol, applied 7 days apart, improves the synchronization of estrous activity and ovulation in goats. Twenty-four cyclic goats were assigned to three groups (n = 8 each). All animals received two doses of 5 mg PGF?? (DIN), 7 days apart; at the time of second injection, they were treated with 100 IU of eCG (PG-eCG), 100 IU of hCG (PG-hCG), or no additional hormone (PG). Although the initial absolute estrous response at 36 h was similar between PG and PG-eCG groups, the PG-eCG treatment achieved a higher cumulative estrous response by 48 h and maintained this advantage at later timepoints (75 and 87.5%, respectively; p 0.05). Follicular monitoring revealed that, in does of the PG–eCG group, eCG administration promoted a more coordinated preovulatory follicular development, particularly between 36 and 72 h after the second DIN injection, and resulted in a concentrated ovulatory peak between 60 and 72 h. This pattern indicates superior synchronization compared with the broader ovulatory window observed in the PG group (36–96 h). In the hCG-treated group, the ovulatory response was distributed across a wide time window, from 36 to 84 h; furthermore, a null response to the treatment was also observed. There were no significant differences in estrous or ovulatory response between the PG and PG-eCG groups (p 0.05); however, both showed higher responses compared with PG-hCG (p 0.05). Goats treated with 100 IU of eCG after a synchronization treatment with a PGF2? analogue showed a better estrous (shorter presentation time) and ovulatory responses. Therefore, it can be an alternative to make hormonal treatments more efficient at low cost. It can also be implemented in FTAI (fixed-time artificial insemination) protocols to positively impact on reproductive parameters.

Reproductive performance in dairy cattle is highly susceptible to heat stress (HS), which negatively affects oocyte quality, fertilization, and early embryonic survival. Embryo transfer (ET) using in vitro-produced embryos may mitigate these adverse effects by allowing early embryonic development to occur under controlled laboratory conditions. Objective: To compare pregnancy rates following ET and artificial insemination (AI) in primiparous Holstein-Friesian cows exposed to chronic HS across seasons. Methods: A total of 275 primiparous Holstein-Friesian cows were assigned to ET (n = 124) or AI (n = 151). All cows underwent standardized hormonal synchronization protocols. Pregnancy diagnosis was performed by transrectal ultrasonography at 30 and 44 days post-service. A generalized linear model with binomial distribution was used to evaluate the effects of each reproductive method and season on pregnancy outcome. Results: The combined overall pregnancy rate was 33.5 %, with no significant differences between ET and AI across seasons (P > 0.05). Logistic regression analysis showed no significant effect of reproductive method (odds ratio = 1.07; 95 % Confidence interval: 0.64–1.78; P = 0.798) or season (P = 0.158) on pregnancy outcome. Although not statistically significant, a numerical trend favoring ET during summer was observed. Conclusions: Under chronic HS conditions, ET using in vitro-produced embryos did not significantly improve pregnancy rates compared with AI.