This review examines genetic markers associated with litter size in goats, a key reproductive trait impacting productivity in small ruminant farming. Goats play a vital socioeconomic role in both low- and high-income regions; however, their productivity remains limited due to low reproductive efficiency. Litter size, influenced by multiple genes and environmental factors, directly affects farm profitability and sustainability by increasing the output per breeding cycle. Recent advancements in genetic research have identified key genes and pathways associated with reproductive traits, including gonadotropin-releasing hormone (GnRH), inhibin (INHAA), Kit ligand (KITLG), protein phosphatase 3 catalytic subunit alpha (PPP3CA), prolactin receptor (PRLR), POU domain class 1 transcription factor 1 (POU1F1), anti-Müllerian hormone (AMH), bone morphogenetic proteins (BMP), growth differentiation factor 9 (GDF9), and KISS1 and suppressor of mothers against decapentaplegic (SMAD) family genes, among others. These genes regulate crucial physiological processes such as folliculogenesis, hormone synthesis, and ovulation. Genome-wide association studies (GWASs) and transcriptomic analyses have pinpointed specific genes linked to increased litter size, highlighting their potential in selective breeding programs. By incorporating genomic data, breeding strategies can achieve higher selection accuracy, accelerate genetic gains, and improve reproductive efficiency. This review emphasizes the importance of genetic markers in optimizing litter size and promoting sustainable productivity in goat farming.

The transforming growth factor-beta (TGF-β) superfamily plays a crucial role in regulating female reproductive traits, particularly litter size, in small ruminants, such as sheep and goats. This review comprehensively examines the molecular mechanisms through which TGF-β superfamily members—including bone morphogenetic proteins (BMPs), growth differentiation factor 9 (GDF9), inhibin (INHA and INHB), and associated signaling genes—influence ovarian follicular development, ovulation rate, and ultimately, litter size. We synthesize recent findings on polymorphisms in key genes, such as BMPR1B, BMP15, GDF9, inhibins and SMADs family genes, across diverse sheep and goat breeds worldwide. The manuscript highlights how specific mutations in these genes create an intricate signaling network that modulates granulosa cell proliferation, follicular sensitivity to FSH, and the prevention of dominant follicle selection. These molecular interactions result in increased ovulation rates and larger litter sizes in prolific breeds. The gene dosage effects observed in heterozygous versus homozygous mutation carriers further illuminate the complex nature of these reproductive regulations. This improved the understanding of the genetic basis for prolificacy provides valuable insights for marker-assisted selection strategies aimed at enhancing reproductive efficiency in small ruminant breeding programs, with significant implications for improving livestock productivity and economic outcomes.

Introduction: Oxidative stress, resulting from environmental changes, significantly affects female fertility. Developing a mouse model to study oxidative stress lays the groundwork for research into human reproductive health and livestock fertility.Materials and methods: In this study, we established and evaluated an oxidative stress model by administering hydrogen peroxide (H₂O₂) to mice. ICR mice of similar age (7–8 weeks old) and average body weight (31.58 ± 1.12 g) were randomly assigned to four groups (A, B, C, and D). Group A served as the control and was injected with a saline solution, while groups B, C, and D received saline solutions containing 0.75%, 1.50%, and 3.0% H₂O₂, respectively, over one week. We measured the body weights of all mice before and after the experimental period.Results and discussion: Our findings showed that the average body weight of mice in groups A and B increased, while groups C and D experienced weight loss. Group C showed a significantly lower average weight gain compared to groups A and B, and group D exhibited an even more pronounced reduction in weight gain. Although group D had a high mortality rate, there was no significant difference in mortality rates among groups B, C, and D. Serum malondialdehyde (MDA) content increased with higher concentrations of H₂O₂, with a significant difference noted between groups C and A. Catalase (CAT) activity in group B was significantly higher than in group A, while superoxide dismutase (SOD) activity in group C was notably elevated compared to groups A and B. Conversely, glutathione peroxidase (GSH-Px) activity in group C was significantly lower than in both group A and group B. Hematoxylin and eosin (HE) staining revealed changes in ovarian morphology and follicle dynamics. The percentage of atretic follicles in group C was significantly higher than in the control group, and group D had a significantly lower total number of healthy follicles compared to the untreated group. Increased H₂O₂ content resulted in a reduction of ovary size and an irregular appearance in group D.Conclusion: Based on our findings, treatment with 1.50% H₂O₂ effectively established an oxidative stress model in mice within 1 week. This model serves as a valuable reference for future clinical studies on oxidative stress and reproductive disorders in female animals and humans.

Semen quality traits, including sperm morphology, sperm shape, sperm count, ejaculate volume, low percentage of motile spermatozoa in semen, and motility, play a crucial role in male reproductive efficiency and fertilization success. This review article highlighted the impact of genetic polymorphisms in genes on semen quality and fertility traits in mammalians. Single nucleotide polymorphisms (SNPs) in these genes were associated with various sperm abnormalities, such as abnormal sperm flagella morphology, reduced motility, impaired DNA integrity, altered antioxidant status, disrupted sperm head–tail junction, spermatogenesis defects, reduced testicular size, and a range of sperm disorders. This comprehensive review of the available literature offers significant insights into the genetic factors influencing semen quality traits, which can contribute to the development of genetic markers and the enhancement of male fertility through assisted selective breeding programs.

Stem cells (SCs), distinguished by their capacity for self-renewal and multipotent differentiation, represent a cornerstone of regenerative medicine. These cells, which can be categorized according to their differentiation potential and developmental origin, have emerged as pivotal elements in both biomedical research and veterinary science. In herbivorous species, stem cell applications have yielded particularly promising advances across multiple domains, including reproductive biotechnology, tissue engineering and regeneration, therapeutic interventions, and immunomodulation. This review synthesizes contemporary research on stem cell biology in five economically significant herbivorous species: bovine, ovine, deer, equine, and camelid. Special emphasis is placed on stem cell isolation methodologies, culture optimization techniques, and the molecular mechanisms governing key signaling pathways. The discussion encompasses both the technical impediments facing stem cell research and the ethical framework necessary for responsible scientific advancement, with particular attention to animal welfare considerations in the development and implementation of stem cell-based technologies.

Litter size is a critical determinant of reproductive efficiency and economic productivity in livestock breeding. Inhibin, a glycoprotein hormone of the transforming growth factor-β (TGF-β) superfamily, plays a pivotal role in regulating follicle-stimulating hormone (FSH) secretion through negative feedback within the hypothalamic–pituitary–gonadal axis. By modulating FSH levels, inhibin influences follicular recruitment, maturation, and ovulation rate—key processes that determine litter size. This review provides a comprehensive analysis of inhibin isoforms (inhibin A and inhibin B), their antagonistic relationship with activin signaling, and their species-specific roles in reproductive regulation. Genetic studies in small ruminants and non-ruminants indicate that polymorphisms in inhibin-related genes, particularly INHA, may contribute to variation in prolificacy-related traits; however, the strength and consistency of these associations differ among species and populations. This review further integrates findings from functional validation studies, particularly in mouse models, demonstrating that partial reduction of inhibin bioactivity can enhance FSH secretion, promote follicular recruitment, and increase ovulation rate and litter size, whereas excessive disruption of inhibin signaling may impair reproductive efficiency. Importantly, the biological effects of inhibin modulation depend on the degree of pathway alteration and the balance between follicular recruitment and prenatal survival. Although inhibin represents an important endocrine regulator of reproductive performance, current genomic evidence suggests that litter-size variation is controlled by multiple interacting pathways, and the contribution of inhibin-related genes requires further functional validation. Future integration of genomic, endocrine, and functional approaches will be essential to clarify the role of inhibin pathways and determine their potential application in sustainable livestock breeding strategies.