Herbivorous livestock, such as cattle, sheep, goats, horses, and donkeys, play a crucial role in agricultural production and possess remarkable resilience to extreme environmental conditions, driven by complex genetic mechanisms. Recent advancements in high-throughput sequencing, genome assembly, and environmental data integration have enabled a deeper understanding of the genetic basis of their environmental adaptation. This review identifies key genes associated with high-altitude, heat, cold, and drought adaptation, providing insights into the molecular mechanisms underlying these traits. By elucidating these genetic adaptations, our study aims to support conservation efforts, inform selective breeding programs, and enhance agricultural productivity, ultimately contributing to sustainable livestock farming and economic benefits for farmers.

Variation in coat color among equids has attracted significant interest in genetics and breeding research. The range of colors is primarily determined by the type, concentration, and distribution of melanin pigments, with the balance between eumelanin and pheomelanin influenced by numerous genetic factors. Advances in genomic and sequencing technologies have enabled the identification of several candidate genes that influence coat color, thereby clarifying the genetic basis of these diverse phenotypes. In this review, we concisely categorize coat coloration in horses and donkeys, focusing on the biosynthesis and types of melanin involved in pigmentation. Moreover, we highlight the regulatory roles of some key candidate genes, such as MC1R, TYR, MITF, ASIP, and KIT, in coat color variation. Moreover, the review explores how coat color relates to selective breeding and specific equine diseases, offering valuable insights for developing breeding strategies that enhance both the esthetic and health aspects of equine species.

Mammary gland development represents a complex and highly regulated biological process that is critical for mammalian reproductive success. This review provides a comprehensive analysis of the molecular, cellular, and hormonal mechanisms governing mammary gland development across distinct developmental stages: embryonic, pubertal, pregnancy, lactation, and involution. Mammary organogenesis is orchestrated by multiple factors, including conserved genetic pathways, endocrine signaling cascades, and environmental stimuli. Drawing primarily from studies in rodents and dairy ruminants, recent advances in molecular biology have elucidated key signaling pathways, including Wnt, Notch, and TGF-β, which provide fundamental insights into mammary epithelial growth and differentiation. Furthermore, we examine the effects of external factors, including thermal stress, photoperiodic variation, and dry period duration on mammary function and lactational performance. The dry period, in particular, serves a critical role in tissue remodeling and preparation for subsequent lactation cycles. Through systematic review of physiological and molecular dynamics across developmental stages, this article identifies key genetic regulators and cellular mechanisms, offering valuable insights for optimizing milk production and composition in agricultural systems.

The major histocompatibility complex (MHC) represents a critical genetic locus that orchestrates adaptive immune responses through antigen presentation and T cell activation, characterized by exceptional polymorphism and species-specific diversity. In herbivores, MHC polymorphisms constitute fundamental determinants of resistance to parasitic, viral, and bacterial infections while serving as crucial indicators of genetic diversity and breeding value in animal populations. Recent advances in high-throughput sequencing technologies, single-cell omics, and population genetics have substantially advanced understanding of MHC gene structure, allelic polymorphism, evolutionary patterns, and associations with disease susceptibility and vaccine responsiveness. This comprehensive review systematically examines the structural characteristics and regulatory mechanisms of MHC genes, their associations with infectious disease resistance, their role in vaccine responses, and their practical applications in molecular breeding programs, conservation genetics, and immunological research. We identify current technical limitations and outline future research directions to establish a robust theoretical foundation for disease resistance breeding and immune regulation strategies in herbivore populations.

Dezhou donkey is a premium indigenous Chinese livestock breed with high economic value for meat, hide and medicinal uses, and growth rate is a core trait determining farming profitability. However, the molecular and metabolic mechanisms underlying divergent growth rates in this breed have not been fully characterized, with no integrated transcriptomic and metabolomic studies reported. Here, 12 age-matched healthy male Dezhou donkeys were assigned to faster-growing (n = 6) and slower-growing (n = 6) groups by average daily gain, followed by plasma transcriptome sequencing and untargeted LC-MS/MS metabolomics. We identified 480 differentially expressed genes, with the slower-growing group enriching in immune/inflammatory/apoptotic pathways, and the faster-growing group in energy metabolism and transmembrane transport. Lipids and lipid-like molecules represented the largest proportion (44.9%) of the differential metabolites; the slower-growing group was enriched in lipid peroxidation and pro-inflammatory mediators, while the faster-growing group was enriched in unsaturated fatty acids and antioxidants. Integrated analysis revealed core pathways (cAMP signaling, arachidonic acid/unsaturated fatty acid biosynthesis) and key candidate genes/metabolites. Our findings clarify that excessive lipid peroxidation and inflammatory imbalance restrict growth, while efficient energy metabolism promotes faster growth, providing theoretical support for genetic improvement and precision nutrition of Dezhou donkeys.