Explore the vast range of titles available.

GnRH is essential for the regulation of mammalian reproductive processes. It regulates the production and release of pituitary gonadotropins, thereby influencing steroidogenesis and gametogenesis. While primarily produced in the hypothalamus, GnRH is also produced in peripheral organs, such as the gonads and placenta. GnRH analogs, including agonists and antagonists, have been synthesized for the reproductive management of animals and humans. This review focuses on the functions of hypothalamic GnRH in the reproductive processes of cattle. In addition to inducing the surge release of LH, the pulsatile secretion of GnRH stimulates the pituitary gland to release FSH and LH, thereby regulating gonadal function. Various GnRH-based products have been synthesized to increase their potency and efficacy in regulating reproductive functions. This review article describes the chemical structures of GnRH and its agonists. This discussion extends to the gene expression of GnRH in the hypothalamus, highlighting its pivotal role in regulating the reproductive process. Furthermore, GnRH is involved in regulating ovarian follicular development and luteal phase support, and estrus synchronization is involved. A comprehensive understanding of the role of GnRH and its analogs in the modulation of reproductive processes is essential for optimizing animal reproduction.

To improve the economic benefits, exogenous hormones are used to control follicular development and synchronize ovulation in the batch flow management of gilts and weaned sows. Equine chorionic gonadotropin (eCG) is widely used to stimulate follicular development in both experimental and farm animals. Despite its effectiveness, several side effects have been found, including the occurrence of follicular cysts, follicular premature luteinization, and increased follicular atresia. As eCG is a heterologous protein, the generation of antibodies has been found in the superovulation of cattle. Moreover, the extraction of eCG from pregnant mare serum raises concerns regarding animal welfare, as well as potential risks for disease transmission. Follicle stimulating hormone (FSH) controls the follicular growth and maturation in the porcine ovary under physiological conditions. In the current study, we developed a novel long-acting recombinant porcine FSH (rpFSH-pFc) consisting of porcine FSH and porcine fragment crystallizable (Fc) via (G4S) 3 linker by using the available protein fusion technology to control the follicular development and maturation. The results of pharmacokinetic studies indicated that rpFSH-pFc exhibited a prolonged half-life in both rats and sows. The efficacy of rpFSH-pFc was confirmed by cAMP level evaluation and germinal vesicle breakdown (GVBD) analysis in vitro. Through ovarian weight gain, superovulation and fertility testing assays, our results revealed that a single rpFSH-pFc treatment could effectively promote follicular development and maturation in vivo. Meanwhile, the mRNA expression levels of the target genes associated with follicular development, maturation and ovulation were significantly up-regulated after rpFSH-pFc treatment. Taken together, our results revealed that rpFSH-pFc could bind to the FSH receptor, stimulate follicular growth and development in female mice, and possess a prolonged half-life in both rats and sows. These characteristics suggest that rpFSH-pFc may be an ideal candidate for promoting follicular growth and development in livestock production.

This study evaluated the ovarian responses and corpus luteum (CL) functionality in Barbados Blackbelly × White Virgin Island crossbred hair sheep subjected to two estrous synchronization protocols in a tropical grazing environment. A total of 40 non-lactating ewes, between 2 and 4 years of age, were randomly assigned to one of two treatment groups. The CIDR + PG group ( n  = 20) received a 7-day intravaginal CIDR device containing 0.3 g of progesterone, followed by an intramuscular injection of 10 mg dinoprost (PG analogue) upon removal of the device. Conversely, the double PG group ( n  = 20) received two intramuscular injections of 10 mg dinoprost, spaced 10 days apart. Ovarian structures were monitored via transrectal ultrasonography over a 21-day period, and blood samples were collected periodically to determine plasma progesterone levels. The proportion of ewes that ovulated was comparable between groups: 80% (16/20) in CIDR + PG and 90% (18/20) in the double PG group. The average interval from treatment to ovulation, inter-ovulatory interval, and preovulatory follicle size did not differ between the groups. Notably, the CL area was significantly larger in the CIDR + PG group ( p  = 0.002), while progesterone concentrations from day 7 to day 13 were higher in the double PG group ( p  < 0.05). Additionally, CIDR + PG-treated ewes underwent earlier luteolysis, resulting in lower progesterone concentrations during the critical phase for establishing pregnancy. In conclusion, both synchronization protocols effectively induced ovulation; however, the CIDR + PG protocol led to earlier CL regression, which may compromise progesterone support during early gestation and negatively impact reproductive performance in tropical hair sheep.

Fifteen cyclic, multiparous goats were equally stratified and received the common Ovsynch protocol (GPG: intramuscular, IM, injection of 50 mg gonadorelin, followed by an IM injection of 125 µg cloprostenol 7 days later, and a further IM injection of 50 mg gonadorelin 2 days later) or the Ovsynch protocol using nanofabricated hormones with the same dosages (NGPG) or half dosages (HNGPG) of each hormone. The ovarian structures and ovarian and luteal artery hemodynamic indices after each injection of the Ovsynch protocol using B-mode, color, and spectral Doppler scanning were monitored. Levels of blood serum progesterone (P4), estradiol (E2), and nitric oxide (NO) were determined. After the first gonadotrophin-releasing hormone (GnRH) injection, the number of large follicles decreased (p = 0.02) in NGPG and HNGPG, compared with GPG. HNGPG resulted in larger corpus luteum (CL) diameters (p = 0.001), and improved ovarian and luteal blood flow, compared with GPG and NGPG. Both NGPG and HNGPG significantly increased E2 and NO levels compared with GPG. HNGPG increased (p < 0.001) P4 levels compared with GPG, whereas NGPG resulted in an intermediate value. After prostaglandin F2α (PGF2α) injection, HNGPG had the largest diameter of CLs (p = 0.001) and significantly improved ovarian blood flow compared with GPG and NGPG. Both NGPG and HNGPG increased (p = 0.007) NO levels, compared with GPG. E2 level was increased (p = 0.028) in HNGPG, compared with GPG, whereas NGPG resulted in an intermediate value. During the follicular phase, HNGPG increased (p = 0.043) the number of medium follicles, shortened (p = 0.04) the interval to ovulation, and increased (p < 0.001) ovarian artery blood flow and levels (p < 0.001) of blood serum P4, E2, and NO, compared with GPG and NGPG. During the luteal phase, the numbers of CLs were similar among different experimental groups, whereas the diameter of CLs, luteal blood flow, and levels of blood serum P4 and NO increased (p < 0.001) in HNGPG, compared with GPG and NGPG. Conclusively, the nanodelivery system for the Ovsynch protocol could be recommended as a new strategy for improving estrous synchronization outcomes of goats while enabling lower hormone dose administration.

The study was conducted to evaluate the effect of two synchronization protocols with prostaglandins (PGF 2α ) on Boran cattle. This study comprised 122 cows and 56 heifers. A uniform system was employed for handling each experimental animal. All 178 animals were administered a single dose of PGF 2α , and those not responding to the initial injection received a second PGF 2α injection after 11 days. The calculation of the conception rate involves determining the number of animals in estrus, those that undergo insemination, and subsequently conceive. A logistic regression analysis was performed to test the effectiveness of the protocols used in estrus response and conception rate. The study's results reveal that a total of 162 animals (91.01%) responded positively to PGF 2α injection. Among these, 62.35% (comprising 62.07% for a single dose and 63.04% for a double dose) successfully conceived. Neither injection protocols nor parity demonstrated any significant impact on estrus response or conception rate (P > 0.05). In conclusion, regardless of parity or injection protocols, PGF 2α injection is effective in inducing estrus. The 62.34% overall conception rate surpassed the national average, suggesting the success of PGF 2α in synchronizing estrus among Boran cows and heifers.

This study evaluated the implementation of reproductive technologies and their effects on pregnancy rates (PRs) and calving distribution. Producers (n = 11) were enrolled in Level 1 or 2 and subsequently transitioned to Level 2 or 3. Level 1: females were exposed to natural service (NS) only versus estrous synchronization (7d-CIDR) before NS (SynNS). Level 2: SynNS versus fixed-time artificial insemination (SynAI; 7d-CO-Synch + CIDR) with conventional semen. Level 3: conventional versus sex-skewed semen (FTAI-con and FTAI-sexed, respectively). Artificial insemination occurred 60–66 h post CIDR removal (SynAI; FTAI-con; FTAI-sexed) and bulls were introduced on d 0 (NS and SynNS) or 10–14 d post artificial insemination (SynAI; FTAI-con; FTAI-sexed). Breeding season PRs did not differ between treatments (p > 0.50). In Level 2, SynNS had greater 21 d PRs compared to SynAI (p < 0.01). For Level 3, FTAI-con had greater 21 d PRs compared to FTAI-sexed (p < 0.01). In Level 1, the proportion of cows that calved by day 14 was greater for SynNS compared to NS (p < 0.01). In Level 2, SynAI had a greater proportion calved by day 7 (p = 0.01); however, SynNS had a greater proportion calved by day 21 and 42 (p < 0.01). In Level 3, FTAI-con had a greater proportion calved by day 14 and 21 (p < 0.01) compared to FTAI-sexed. In conclusion, reproductive technologies altered the calving distribution with more calves born earlier.

Buffalo occupies a leading position as a major livestock commodity and is the primary milk-producing animal in many countries like Italy, China, India, Pakistan, Bangladesh, and Nepal. Buffalo farming emphasizes the significance of effective reproductive strategies. Among effective reproductive strategy, artificial insemination has a significant influence on herd's genetic progress. Nonetheless, buffaloes exhibit unique reproductive behavior, which complicates the insemination process. These animals demonstrate inconsistent periods (ranging from 6–48 h) of mounting acceptance. Therefore, timed artificial insemination (TAI) has surfaced as a useful technique for advancing buffalo breeding initiatives and omits the need for heat detection. TAI enhances reproductive management and genetic progress in buffaloes by synchronizing estrus and optimizing insemination timing. This review focuses on examining buffalo reproductive physiology, particularly emphasizing estrus synchronization protocols, ovulation, and TAI. We also provide a brief description of the factors influencing TAI success, such as hormonal treatments and environmental conditions. This review underscores TAI's importance identifies areas for further research and development and reinforces its central role in sustainable buffalo farming.

Artificial insemination (AI) is a key reproductive biotechnology for genetic improvement in sheep. However, its efficiency remains lower and more variable than in most other livestock species. This review critically synthesizes the historical foundations of sheep AI, including methodological principles established by the Soviet school, and evaluates how these concepts have been further developed and adapted to contemporary reproductive biology. Particular emphasis is placed on estrous synchronization protocols, semen processing and cryopreservation, and insemination techniques. We highlight how anatomical constraints of the ovine cervix, seasonal reproductive physiology, and species-specific characteristics of ram sperm collectively limit fertility outcomes, especially when frozen–thawed semen is used. Comparative analysis of cervical, transcervical, and laparoscopic insemination methods indicates that laparoscopic AI remains the most reliable approach, although recent advances in catheter design and semen handling have improved the feasibility of less invasive techniques. This review further discusses emerging approaches, including sperm sex-sorting, alternative recovery methods, and early-stage spermatogonial stem cell–based technologies, emphasizing both their potential applications and current limitations. Overall, the available evidence suggests that future progress in sheep AI will depend on the integrated optimization of hormonal synchronization, semen preservation, and insemination strategies, rather than on isolated technical innovations.

The purpose of this study is to compare five protocols of estrous synchronization for Hu ewes to obtain the most effective and economical protocol, to apply the advantageous scheme in large-scale sheep farming. Healthy multiparous Hu ewes ( n = 150) were randomly divided into five groups, and all ewes were administered fluorogestone acetate (FGA, 45 mg) vaginal sponge. The sponges of the first three groups (Groups I, II, and III) were removed on the 11th day, and 0.1 mg of PGF 2α was injected intramuscularly on the ninth day. Group I received 6 μg of gonadotropin-releasing hormone (GnRH) by intramuscular injection at 36th h after withdrawal of the sponge. Group II was injected 330 IU of pregnant mare serum gonadotropin (PMSG) on the ninth day. The combination of 6 μg of GnRH and 330 IU of PMSG was treated in Group III at the same time as Group I and Group II. The sponges of the latter two groups (Groups IV and V) were removed on the 13th day, and 330 IU of PMSG was injected intramuscularly simultaneously. PGF 2α (0.1 mg) was administered on the 12th day in Group IV. All ewes were detected for estrus at 24, 36, 48, 60, and 72 h after the sponge removal. The loss of sponge and vaginitis was recorded when the sponge was withdrawn. Cervical artificial insemination (AI) was performed with fresh semen of Dorper rams diluted with skimmed milk. After 30 days of insemination, the conception was detected with a veterinary B-ultrasound scanner. The lambing status of all ewes and the cost of drugs for estrous synchronization in each group were recorded. The results showed the following: (1) on the whole, the average percentage of estrous ewes in the period of 24–36 h and 36–48 h after removal was significantly higher than other three periods and that of the period of 60–72 h was significantly lower than the first three periods after removal; (2) there was no significant difference in percentages of estrous ewes in any of the five time periods, sponge loss rate, vaginitis rate, total percentage of estrous ewes, conception rate, single lambing rate, twinning rate, and multiple lambing rate of ewes among five protocols; (3) total percentage of estrous ewes and conception rate were more than or equal to 80% in the Groups II and III, and the twinning lamb rate of the Group II protocol was 70%; (4) there was no difference in lambing rate of ewes among Groups II, III, IV, and V; (5) the Group III had the highest drug cost of 22.5 CNY. In conclusion, considering the lambing rate, twinning lamb rate, and drug cost for estrous synchronization, Group II was the most advisable for application and promotion in large-scale sheep farms among these five protocols of estrus synchronization.

This study was carried out to compare the effects of intravaginal FGA sponges to synchronize estrus on reproductive performance of the Karadi and Arabi ewes , 30 for each breed at 2-4 years during the breeding season were used. Ewes from each breed were equally and randomly distributed into three groups. The first group was treated with vaginal sponges saturated with (40 mg) of FGA within a period of 14 days (T1). The second group administrate with the FGA and is injected with a dose of 400 IU of the PMSG hormone  (T2). The third group treated with a dose of 0.5 ml/head of PGF2α hormone (T3)  on the day of sponge removal, was injected at. The result of the study showed a non-significant increase in the estrous rate, fertility rate and Prolificacy between Different groups regardless type of breed. Different treatments showed a significant difference (p≤ 0.05) in the pregnancy length, the T3 group showed the shortest period and the highest lambing number in comparison with T1 and T2. Birth weight increased significantly (p≤ 0.05) in T1 and T3 (4.413, 4.310) kg respectively with a slight difference between the Karadi and Arabi breeds. In conclusion, exogenous hormonal treatments in a combination of FGA sponge using PMSG and PGF2α improved reproduction parameters.