Sexual behaviour, semen quality and fertility of young Border Leicester rams administered melatonin during spring

From spermatogenesis to fertilisation: the role of melatonin on ram spermatozoa

This review presents recent findings on the effect of melatonin on ram spermatozoa. This hormone regulates seasonal reproduction in the ovine species through the hypothalamic-pituitary-gonadal axis, but it also exerts direct effects on spermatogenesis, seminal quality and fertility. In the testis, melatonin stimulates blood flow to this organ, but it also appears to be involved in the differentiation of spermatogonial stem cells and the secretion of testosterone through the MT1 and MT2 receptors. In the epididymis, this hormone modulates sperm maturation and the secretory activity of epidydimal epithelial cells. In addition, the antioxidant activity of melatonin may protect spermatozoa from oxidative damage during their formation in the testis and their maturation in the epididymis. After ejaculation, the melatonin present in seminal plasma may also protect sperm from oxidative damage and premature capacitation and may improve seminal quality. Finally, once the sperm begins its transit through the female genital tract, melatonin may modulate sperm capacitation. Thus, melatonin could have a bimodal activity in ram sperm capacitation, so high concentrations, such as those in seminal plasma, have a decapacitating effect. In contrast, low concentrations, such as those present in the female reproductive tract, may promote it, likely through interaction with MT2 receptors. In addition, melatonin could also be involved in chemotaxis and fertilisation, although further studies are needed to elucidate the specific role of melatonin in these processes. Finally, the effect of latitude and melatonin receptor gene polymorphisms in ram reproduction is also discussed.

Administration of melatonin nanoparticles improves testicular blood flow, echotexture of testicular parenchyma, scrotal circumference, and levels of estradiol and nitric oxide in prepubertal ossimi rams under summer heat stress

Environmental heat stress (HS) impairs reproductive efficiency in farm animals. This study investigated, for the first time, how the melatonin and melatonin nanoparticles treatment affected the testicular hemodynamics, testicular volume, echotexture [Pixel intensity (PIX) and integrated density (IND)], scrotal circumference, serum concentration of testosterone (T), estradiol (E2), nitric oxide (NO), and total antioxidant capacity (TAC) in prepubertal Ossimi ram lambs in hot climatic conditions. The lambs undergoing examination had a temperature humidity index (THI) of 87.05 ± 1.70, indicating severe HS condition. Fifteen prepubertal Ossimi ram lambs were exposed to a single s.c injection of either nano melatonin (nano melatonin group; 20 mg/ram; n = 5) or melatonin suspended in two ml of corn oil (melatonin group; 40 mg/ram; n = 5) or two ml of corn oil (control group; n = 5). Blood collection and ultrasonographic assessment of the testes and supratesticular arteries (STAs) were conducted immediately before treatment (W0) and once weekly for six successive weeks after nano melatonin and melatonin injection (W1-W6). Results revealed decreases (P < 0.05) in the Doppler indices (resistive index; RI and pulsatility index; PI) of the testicular arteries at most time points of the study in the nano melatonin and melatonin groups. PIX of testicular parenchyma was significantly increased (P ˂ 0.05) in the treated groups compared to the control one. IND of testicular parenchyma increased significantly in the nano melatonin group compared to the melatonin and control groups. Testicular volume and scrotal circumference significantly increased (P < 0.05) in nano melatonin and melatonin groups compared to the control one. T concentration did not significantly (P > 0.05) change in the treated groups compared to the control group. E2, NO, and TAC concentrations increased (P < 0.05) in the treated groups compared to the control one. In conclusion, this study extrapolated that administrations of melatonin or nano melatonin can ameliorate the effects of environmental HS in prepubertal Ossimi ram lambs with a more protective effect and lower dose of nano melatonin.

Systematic review of hormonal strategies to improve fertility in rams

Reviewing the current state of knowledge on reproductive performance and productive traits in rams has many advantages. First, the compilation of this information will serve as a literature resource for scientists conducting research around the world and will contribute to the understanding of the data collected and interpreted by researchers on the different hormonal strategies used to improve reproductive performance in rams. Second, it will allow scientists to identify current knowledge gaps and set future research priorities in ram reproduction. Rams play an important role in the global flock economy, but their reproductive analysis has been limited in the use of hormonal technologies to increase the productivity of sheep flocks. In this review, we cite the most important works on six hormones that, in one way or another, modify the hypothalamus-pituitary-gonadal axis, at different doses, in and out of the reproductive season, breeds, application methods, among other factors. The overall aim is to increase the reproductive efficiency of rams in different scenarios and, in some cases, of other species due to the lack of limited information on rams.

Single-Cell Transcriptome Sequencing Reveals Molecular Expression Differences and Marker Genes in Testes during the Sexual Maturation of Mongolian Horses

This study aimed to investigate differences in testicular tissue morphology, gene expression, and marker genes between sexually immature (1-year-old) and sexually mature (10-year-old) Mongolian horses. The purposes of our research were to provide insights into the reproductive physiology of male Mongolian horses and to identify potential markers for sexual maturity. The methods we applied included the transcriptomic profiling of testicular cells using single-cell sequencing techniques. Our results revealed significant differences in tissue morphology and gene expression patterns between the two age groups. Specifically, 25 cell clusters and 10 cell types were identified, including spermatogonial and somatic cells. Differential gene expression analysis highlighted distinct patterns related to cellular infrastructure in sexually immature horses and spermatogenesis in sexually mature horses. Marker genes specific to each stage were also identified, including APOA1, AMH, TAC3, INHA, SPARC, and SOX9 for the sexually immature stage, and PRM1, PRM2, LOC100051500, PRSS37, HMGB4, and H1-9 for the sexually mature stage. These findings contribute to a deeper understanding of testicular development and spermatogenesis in Mongolian horses and have potential applications in equine reproductive biology and breeding programs. In conclusion, this study provides valuable insights into the molecular mechanisms underlying sexual maturity in Mongolian horses.

Impact of melatonin administration on sperm quality, steroid hormone levels, and testicular blood flow parameters in small ruminants: A meta-analysis

Background and Aim

The impact of exogenous melatonin on the sperm quality of small ruminants is controversial. Therefore, this study aimed to synthesize previous findings on the influence of melatonin injection on sperm quality, steroid hormones, and testicular blood flow in small ruminants.

Materials and Methods

Thirty studies were analyzed by computing the raw mean difference (RMD) as the effect size between the control and melatonin treatment groups, using the inverse of the variance for the random-effect model of the method of moments by DerSimonian and Laird. We assessed heterogeneity among studies using Q test. I2 statistic was used to classify the observed heterogeneity. We used Egger's regression method to indicate publication bias.

Results

Melatonin injection (p < 0.05) affected sperm concentration (RMD = 0.42 × 109/mL), morphology (RMD = 2.82%), viability (RMD = 2.83%), acrosome integrity (RMD = 4.26%), and DNA integrity (RMD = 1.09%). Total motility (RMD = 5.62%), progressive motility (RMD = 7.90%), acrosome integrity (RMD = 8.68%), and DNA integrity (RMD = 2.01%) of post-thawed semen in the melatonin-treated group were also increased (p < 0.05). Similarly, treatment with melatonin (p < 0.05) enhanced total motility (RMD = 5.78%), progressive motility (RMD = 5.28%), curvilinear velocity (RMD = 4.09 μm/s), straight-line velocity (RMD = 5.61 μm/s), and average path velocity (RMD = 4.94 μm/s). Testosterone (RMD = 1.02 ng/mL) and estradiol 17-ß levels (RMD = 0.84 pg/mL) were elevated (p < 0.05) in the melatonin-injected group. Melatonin implantation ameliorated testicular blood flow, as indicated by a significant reduction (p < 0.05) in the resistive index (RMD = 0.11) and pulsatility index (RMD = -0.15).

Conclusion

Melatonin administration can increase the reproductive performance of small male ruminants.

Effects of the breeding season, birth type and sex on growth and reproductive performances of sheep breeds

The study aimed at determining the effects of breed type, breeding season, sex and type of birth on the growth and reproductive traits of lambs. Two ewe breed types (Gellaper and Swakara) and four ram breed types (Damara, Dorper, GeDo and Swakara) were used. Two lambing seasons, spring (March-May) and autumn (September-November), were considered. Gellaper-based lambs born in autumn had higher (P < 0.05) mean birth weight (4.58 kg) compared to spring-born lambs (3.43 kg). Ram lambs were heavier (P < 0.05) than ewe lambs at weaning and post-weaning age. Singletons were heavier than twins (P < 0.05) at birth, weaning and breeding. Single and autumn-born lambs had a higher average daily gain (ADG) than spring-born lambs (P < 0.05). Ram lambs had a higher pre-weaning and overall ADG (P < 0.05) compared with ewe lambs. Swakara-based lambs gained more from weaning to mating compared to Gellaper-based lambs (P < 0.05). The conception, lambing and annual reproductive rate were all influenced by breed type and season (P < 0.05). Swakara-based lambs had higher reproductive capabilities, while Gellaper-based lambs grew faster but take longer to breed type; autumn lambing gave rise to low birth weights but heavier lambs at weaning and post-weaning, hence suitable for mutton production.