Associations among the largest follicle, preovulatory estradiol concentrations, and predominant vaginal epithelial cells at the completion of hormonal ovarian stimulation for fixed-time artificial insemination in goats

The objective of the present study was to investigate the association among the largest follicle (LF), preovulatory estradiol (E2), and predominant vaginal epithelial cell at the completion of hormonal ovarian stimulation for fixed-time artificial insemination (FTAI) in goats. Thirty-seven crossbred Boer does received gonadotropin-releasing hormone (GnRH) and intravaginal progesterone (P4)-releasing devices (day 0). On day 5, P4 devices were removed and does received prostaglandin F2α and equine chorionic gonadotrophin. On day 7, does received GnRH, and FTAI was undertaken. On day 7, does were divided into three groups, i.e. small-sized (3-3.9 mm; n = 5), medium-sized (4-4.9 mm; n = 8), and large-sized (≥5 mm; n = 24) according to the diameter of the ovarian LF; follicular characteristics (number and diameter) were identified, and blood samples and vaginal smears were collected. The average diameters of total antral follicles and LF and the percentage of superficial cell were greatest in large-sized LF does (p < .01). The average diameters of total antral follicle (r = .68) and LF (r = .71), number of preovulatory follicle (r = .58), and plasma E2 concentrations (r = .61) were positively correlated with the percentage of superficial cells (p < .01). The likelihood of a pregnancy outcome after the FTAI increased by 13.71 times in does with a greater average diameter of antral follicle, 14.18 times with emergence of a large preovulatory follicle, and 36.83 times with a higher percentage of vaginal superficial cells (p < .01). It was concluded that there is a relationship between the cell types of the vaginal epithelium, the diameters of the largest ovarian follicles, and the concentration of E2 in goats subjected to FTAI protocols.

Coping with Oxidative Stress in Reproductive Pathophysiology and Assisted Reproduction: Melatonin as an Emerging Therapeutical Tool

Infertility is an increasing global public health concern with socio-psychological implications for affected couples. Remarkable advances in reproductive medicine have led to successful treatments such as assisted reproductive techniques (ART). However, the search for new therapeutic tools to improve ART success rates has become a research hotspot. In the last few years, pineal indolamine melatonin has been investigated for its powerful antioxidant properties and its role in reproductive physiology. It is considered a promising therapeutical agent to counteract the detrimental effects associated with oxidative stress in fertility treatments. The aim of the present narrative review was to summarize the current state of the art on the importance of melatonin in reproductive physiology and to provide a critical evaluation of the data available encompassing basic, translational and clinical studies on its potential use in ART to improve fertility success rates.

Melatonin promotes the growth and development of lambs by increasing growth hormone and testosterone, targeting on apoptosis signaling pathway and intestinal microflora

Melatonin is an indole-like neuroendocrine hormone. A large number of studies have shown that melatonin can improve production performance of ewes, but it is not clear in lambs. In this study, the growth and development of the 2-month-old lambs implanted with melatonin were monitored for 60 days. The results showed that the growth rate of body weight and body skew length of lambs with melatonin treatment were significantly improved compared to the controls. The similar results were also observed in red blood cell count, hematocrit, red blood cell volume distribution width, the levels of growth hormone, testosterone, immunoglobulin A, immunoglobulin M and albumin. In addition, the cross sectional area of muscle fibers and adipose cells of lambs with melatonin implantation were also significantly increased compared to the controls (P<0.05). To further explore the potential mechanisms, the muscle and adipose tissue were selected for transcriptome sequencing. KEGG enrichment results showed that melatonin regulated the expression of genes related to apoptotic signaling pathway in muscle and adipocytes. Since the intestinal microbiota are involved in the nutritional balance and animal growth, the 16SrRNA sequencing related to the intestinal microbiota was also performed. The data indicated that the structural differences of fecal microflora mainly occur in the pathways of Cardiovascular disease, Excretory system and Signaling molecules and interaction. In brief, melatonin promotes the growth and development of lambs. The potential mechanisms may be that melatonin increased the growth hormone and testosterone mediated apoptosis signaling pathway and regulated intestinal microbial flora. Our results provide valuable information for melatonin to improve the production of sheep husbandry in the future.

Lack of effect of melatonin on ovarian function and response to estrous synchronization and fixed-time AI during the nonbreeding season in lactating dairy buffalo (Bubalus bubalis)

The present study was conducted to examine whether pretreatment with melatonin would enhance ovarian follicular functions and increase response to estrous synchronization and fixed-time AI (TAI) during the nonbreeding season in lactating dairy buffalo. In Experiment 1, buffalo cows without a detectable corpus luteum (CL) were assigned on Day -20 (D-20) to three groups: control (n = 12); melatonin (n = 13); progesterone (P₄) (n = 15). Cows in the melatonin group were implanted with melatonin on D-20. From D0 to D9, there was imposing of an estrous synchronization treatment regimen using either a standard Ovsynch protocol (control, melatonin) or a P₄-based Ovsynch treatment regimen (P₄). There were no differences (P > 0.05) among groups for the presence of a CL at D0, size of the largest follicle at D0, ovulation to GnRH injection at D0 and D9, or the time to ovulation after injection of GnRH at D9. In Experiment 2, there was imposing of the same treatment regimens as in Experiment 1, with inclusion of TAI. Females of the P₄ group had a greater (P = 0.001) pregnancy/AI percentage (60 %) than those in the control (17 %) and melatonin (23 %) groups. Females of the P₄ group also had a larger (P = 0.005) CL at D20 compared with those in the control and melatonin groups. Findings indicate treatment with melatonin for 20 days did not affect ovarian functions or the response to an estrous synchronization treatment regimen and TAI during the nonbreeding season in lactating dairy buffalo.

Greater concentrations of IGF-1 are associated with increasing pregnancy rate in melatonin implanted anestrous Barki ewes

The present study was conducted to determine if increases in IGF-1 concentration, associated with treatment of ewes with melatonin, has beneficial effects on pregnancy rates when there is induction of estrus in anestrous ewes. A total of 120 multiparous lactating ewes were assigned to three groups (n = 10/group). Ewes of Group 1 were treated with a melatonin implant for 42 days followed by insertion of a controlled internal drug release (CIDR) device for 14 days with administration of equine chorionic gonadotropin (eCG) at day of CIDR removal. The ewes of Group 2 were treated with a CIDR and eCG at the same times as ewes of Group 1 and ewes of Group 3 were assigned to an be untreated control group. Melatonin implantation resulted in an increase in IGF-1 concentrations and lesser estradiol (E₂) and triiodothyronine (T₃) concentrations. Ewes of Groups 1 and 2 had the greatest progesterone (P₄) concentration compared ewes of Group 3. The E₂:P₄ ratio was less in ewes of Group 1 compared Group 3. Melatonin implantation of ewes resulted in a greater pregnancy rate compared to treatment with the CIDR and eCG which, in turn, had a greater rate than ewes of the control group. In conclusion, melatonin implantation modulates the hormonal milieu including P₄, E₂, T₃ and IGF-1 in seasonally anestrous ewes. Increased IGF-1concentrations, as a result of melatonin treatment, are associated with a greater percentage pregnancy rate when there is treatment of anestrous ewes to induce onset of estrus.

Exogenous and endogenous factors in seasonality of reproduction in buffalo: A review

Seasonal breeding in buffalo is influenced by exogenous (photoperiod, climate, nutrition, management) and endogenous (hormones, genotype) factors. Buffalo are negatively photoperiodic and show a natural increase in fertility during decreasing day length. The hormone melatonin is produced by the pineal gland and has a fundamental role in photoperiodic time measurement within the brain. This drives annual cycles of gonadotropin secretion and gonadal function in buffaloes. Some melatonin is released into the systemic circulation and, together with peripherally produced melatonin, acts at somatic tissues. In the ovaries and testes of buffalo, melatonin acts as an antioxidant and scavenges oxygen free radicals to reduce both oxidative stress and apoptosis. This has beneficial effects on gametogenesis and steroidogenesis. Female buffalo treated with melatonin show an improved response to estrus synchronization protocols in out-of-season breeding. Melatonin acts through melatonin receptors MT₁ and MT₂ and the gene for MT₁ (MTNR1A) is polymorphic in buffaloes. Single nucleotide polymorphisms (SNPs) in gene MTNR1A have been associated with fertility in female buffalo. The knowledge and tools are available to lift the reproductive performance of buffalo. This is highly important as the global demand for nutritious buffalo food products has undergone a sharp rise, and continues to grow. Buffalo can make an important contribution to affordable, nutritious animal protein. This will help address global nutritional security.

Research progress on the role of melatonin and its receptors in animal reproduction: A comprehensive review

Melatonin and its receptors play a crucial role in the regulation of the animal reproductive process, primarily in follicular development. However, the role that melatonin performs in regulating hormones related with reproduction remains unclear. Melatonin and its receptors are present both in female and male animals' organs, such as ovaries, heart, brain and liver. Melatonin regulates ovarian actions and is a key mediator of reproductive actions. Melatonin has numerous effects on animal reproduction, such as protection of gametes and embryos, response to clock genes, immune-neuroendocrine, reconciliation of seasonal variations in immune function, and silence or blockage of genes. The growth ratio of reproductive illnesses in animals has raised a remarkable concern for the government, animal caretakers and farm managers. In order to resolve this challenging issue, it is very necessary to conduct state-of-the-art research on melatonin and its receptors because melatonin has considerable physiognomies. This review article presents a current contemporary research conducted by numerous researchers from the entire world on the role of melatonin and its receptors in animal reproduction, from the year 1985 to the year 2017. Furthermore, this review shows scientific research challenges related to melatonin receptors and their explanations based on the findings of 172 numerous research articles, and also represents significant proficiencies of melatonin in order to show enthusiastic study direction for animal reproduction researchers.