During the estrous cycle of mammals， a large number of follicles are recruited. Typically， only one follicle is selected for dominance and ovulation in monotocous （single-offspring） species per cycle， while only a few follicles are selected for dominance in polytocous （multiple-offspring） species. The vast majority of the remaining follicles undergo atresia. In recent years， significant progress has been made in research focusing on follicular dominance selection， although the underlying mechanisms have not yet been fully elucidated. Insulin-like growth factor 1 （IGF-1） has been demonstrated to play a crucial role in follicular development. This review summarizes the roles and mechanisms of IGF-1 in mammalian follicular development， focusing on its involvement in dominant follicle selection， promotion of follicular growth and development， inhibition of granulosa cell apoptosis， and maintenance of normal reproductive performance in female mammals.

Ovarian folliculogenesis is fundamental to the reproductive activity of female mammals， encompassing the formation of primordial follicles， follicular recruitment， dominant follicle selection， ovulation of mature follicles， and the follicular atresia process that persists throughout development. Ferroptosis， a novel form of regulated cell death， plays a critical role in follicular development， particularly during atresia. This review systematically explores the molecular mechanisms of ferroptosis， emphasizing its impact on follicular atresia， primordial follicle activation， and oocyte maturation， as well as the regulatory effects of antioxidants on ferroptosis. The aim is to provide a theoretical reference for further research in this domain.

Animal mammary bioreactors utilize mammalian-specific lactoprotein gene promoters to direct the efficient and specific expression of exogenous genes in the animal mammary gland， ultimately obtaining protein expression products through the secretory function of the mammalian mammary gland. This article focuses on the application progress and research prospects of animal mammary bioreactors， providing theoretical reference value for future research and industrial development of animal mammary bioreactors. Through literature review and practical research， a brief overview is provided from the aspects of the principle， characteristics， target animal selection， application fields， challenges faced， and development prospects of animal mammary bioreactors. Different animal mammary bioreactors have their own advantages and disadvantages， and target animals can be reasonably selected according to actual needs and production practices. Compared with other traditional expression systems， mammary bioreactors are a novel expression mode with advantages such as high yield， easy purification， low cost， high biological activity， and high safety， and are widely used in improving animal milk quality， producing recombinant pharmaceutical proteins， making antibodies， synthesizing genetic engineering vaccines， and other fields. Although many influencing factors of mammary bioreactors are still unknown， there are some problems that urgently need to be solved， and challenges are also faced. However， with the rise of gene editing technologies such as CRISPR/Cas9， as long as technological innovation and research and development investment are continuously increased， their application prospects are very broad.

Tetraploid embryo technology is an important tool for livestock genetic breeding and biomedical research， and its application potential is becoming more and more prominent. In this paper， we systematically review the key technologies， bottlenecks and future development directions of tetraploid in vitro embryo production in livestock. It focuses on the induction methods （e.g.， physical， chemical， and biological methods）， optimization of in vitro culture systems， and factors affecting the developmental efficiency of tetraploid embryos of major livestock species， such as pigs， cows， and sheep. By comparing the developmental characteristics of tetraploid embryos from different species， we reveal the core limiting factors such as abnormal activation of the embryonic genome and defective placental development. Combined with the cutting-edge technologies of gene editing and embryo-like culture， the application of this echnology in the fields of efficient breeding， disease modeling and xenotransplantation is envisioned， with a view to providing theoretical references and technological guidance for related research.

Excessive fat accumulation in the ovine caudal region compromises feed efficiency and reproductive performance， consequently elevating production costs and diminishing producer incomes. Furthermore， tail docking fails to mitigate caudal adiposity； instead， it promotes ectopic fat deposition within the gluteal musculature. Consequently， the development of thin-tailed sheep populations through genome-wide selection has emerged as a critical objective for sheep breeders， and the key to addressing this challenge lies in identifying genes associated with ovine tail phenotypes. This review systematically synthesizes current knowledge on the functions of key genes （e.g. BMP2， PDGFD， and TBXT） and their epigenetic regulatory mechanisms involved in regulating sheep tail types， focusing on both adipogenesis and tail vertebrae length. Additionally， it explores the conservation value of fat-tailed sheep as a unique genetic resource. These findings provide a theoretical foundation for the genomic selection and breeding of sheep breeds with specific tail conformations.

Methionine （Met）， as an essential amino acid for ruminants， plays a critical role in production performance， reproductive efficiency， immune function， and regulation of the rumen environment. However， dietary Met is susceptible to degradation by rumen microbes， leading to insufficient absorption in the small intestine. To address this， rumen-protected methionine （RPM） is developed through coating technology or chemical modification， effectively reducing rumen degradation rates and enhancing its utilization in the small intestine. Supplementation with RPM improves ruminant production performance， optimizes rumen microbial flora， enhances nitrogen balance， boosts reproductive performance， regulates immune gene expression， and strengthens antioxidant capacity. This article systematically reviews the technological principles of RPM and its application progress in ruminant production， providing a theoretical foundation for the practical implementation of RPM.

The rapid development of large-scale and intensive livestock and poultry farming has led to a significant increase in the frequency of heat stress， which results in a series of harms to the production performance and physical health of livestock and poultry. Studies have found that the body damages of livestock and poultry caused by heat stress are closely related to endotoxins. Under heat stress conditions， the increase in peripheral blood volume leads to insufficient blood supply for the gastrointestinal tract， resulting in damages to its barrier function. Consequently， an increasing translocation of bacterial endotoxins into the blood system would lead to damages to various organs of the body. This article reviews the generation of endotoxin in livestock and poultry under heat stress conditions， its damage to the bodies of livestock and poultry under heat stress conditions， and the research progresses on the relevant body damages and mechanisms， with the aim of providing an innovative reference for the prevention and control of endotoxins hazards in livestock and poultry exposed to heat stress.

Bile acids， which are significant metabolites， are generated by the liver and conveyed to the intestine. Microorganisms in the intestine modify and process bile acids into secondary bile acids. Historically， it was believed that bile acids were engaged in the absorption and metabolism processes of lipids and fat-soluble vitamins. An increasing number of studies have shown that bile acids can act as multiple signaling metabolites， which are essential for maintaining bile acid homeostasis， enterohepatic circulation， metabolism， intestinal barrier integrity， and intestinal mucosal immune homeostasis by regulating bile acid-related receptors and interactions with the microbiota. Unique lymphocyte populations cooperate with each other to jointly maintain the stability of the intestinal immune system. Among these elements， the equilibrium between pro-inflammatory T helper 17 cells （T_H17） and anti-inflammatory regulatory T cells （T_reg） holds particular significance. It is of great importance in safeguarding the homeostasis of the intestinal immune system. This article reviews the complex relationship and latest research progress between bile acids， intestinal microorganisms and intestinal mucosal immunity from the following three aspects： the interaction between bile acids and intestinal microorganisms， bile acid-related receptors， and the balance between T_H17/T_reg cells， in order to provide a theoretical basis for revealing the physiological functions of bile acids and their application in animal production.

The intestine， as the organ responsible for food digestion and nutrient absorption within the body， its structural and functional integrity is of critical importance for health maintainance. The brush border is an essential intestinal structure that， through its highly ordered array of microvilli， greatly expands the absorptive surface area and plays a central role in mediating nutrient transport， maintaining epithelial homeostasis， and forming a physical barrier defense. A clear understanding of the brush border’s microstructure is of great value for both basic and clinical research related to intestinal function. This article systematically reviews the structural components of the brush border and the ultrastructure of microvilli， with a focus on the actin core bundles within microvilli； the cross-linking roles of bundling proteins such as Fimbrin， Villin， and Espin-1； the mechanical stabilization and dynamic regulation provided by the terminal web through proteins including Calmodulin， Spectrin， and Myosin； and the regulatory function of the intermicrovillar adhesion complex in the ordered assembly of microvilli. By offering a systematic overview of microvillar architecture and functional proteins， this work provides an important theoretical basis for deep understanding the assembly and regulatory mechanisms of small-intestinal microvilli and their targeted modulation in intestinal diseases.

Bisphenol A （BPA） is an environmental endocrine disrupting chemical which widely used in plastic production. Due to the large-scale production and use of BPA， it poses a threat to human and animal health. This article systematically sorts out the research results on the toxic effects of BPA at home and abroad in recent years， and comprehensively reviews the sources and routes of BPA exposure， its metabolic transformation in animals， as well as the progress of its toxic effects on livestock and poultry health. It will help to improve the understanding of the toxicity of BPA， and is expected to provide valuable reference materials for in-depth studies on the animal toxicity mechanism of BPA and prevention of the hazards of BPA in livestock and poultry farming.