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Simple Summary: Color and body size traits are considered the key parameters influence the economic value of animals. In recent years, advancement in the genetic basis of coat colors in equines has received considerable attention among animal breeders. In addition, coat color plays a significant role in breed identification and selection, as well as animal health and disease. The current review concisely provides information on the role of melanin pigments and key candidate genes associated with coat color phenotypes in equines. Furthermore, the review also highlights the importance of coat color in equine breeding and health. 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. [ABSTRACT FROM AUTHOR]

Simple Summary: This study investigates the impact of DNA methylation on collagen deposition in the skin of Dezhou donkeys, a breed valued for its thick, flexible skin with medicinal properties. Utilizing whole genome bisulfite sequencing (WGBS) and RNA sequencing (RNA-seq), the research analyzes the epigenetic landscape and gene expression profiles across three developmental stages of Dezhou donkeys. The study identifies numerous differentially methylated genes related to collagen deposition, such as COL1A1, COL1A2, and MMPs, highlighting an inverse relationship between gene expression and DNA methylation near transcription start sites. The findings of our study reveal the significant regulatory role of DNA methylation in skin collagen deposition, offering insights for genetic improvement and selective breeding to enhance skin quality in Dezhou donkeys. Our current research adds to the foundational knowledge of collagen deposition mechanisms, contributing to the fields of molecular biology and animal husbandry. DNA methylation represents a predominant epigenetic modification with broad implications in various biological functions. Its role is particularly significant in the process of collagen deposition, a fundamental aspect of dermal development in donkeys. Despite its critical involvement, the mechanistic insights into how DNA methylation influences collagen deposition in donkey skin remain limited. In this study, we employed whole genome bisulfite sequencing (WGBS) and RNA sequencing (RNA-seq) to investigate the epigenetic landscape and gene expression profiles in the dorsal skin tissues of Dezhou donkeys across three developmental stages: embryonic (YD), juvenile (2-year-old, MD), and mature (8-year-old, OD). Our analysis identified numerous differentially methylated genes that play pivotal roles in skin collagen deposition and overall skin maturation, including but not limited to COL1A1, COL1A2, COL3A1, COL4A1, COL4A2, GLUL, SFRP2, FOSL1, SERPINE1, MMP1, MMP2, MMP9, and MMP13. Notably, we observed an inverse relationship between gene expression and DNA methylation proximal to transcription start sites (TSSs), whereas a direct correlation was detected in regions close to transcription termination sites (TTSs). Detailed bisulfite sequencing analyses of the COL1A1 promoter region revealed a low methylation status during the embryonic stage, correlating with elevated transcriptional activity and gene expression levels. Collectively, our findings elucidate key genetic markers associated with collagen deposition in the skin of Dezhou donkeys, underscoring the significant regulatory role of DNA methylation. This research work contributes to the foundational knowledge necessary for the genetic improvement and selective breeding of Dezhou donkeys, aiming to enhance skin quality attributes. [ABSTRACT FROM AUTHOR]

Background: At present, donkey meat in the market shows an imbalance between supply and demand, and there is an urgent need to cultivate a meat-type Dezhou donkey breed. On the one hand, it can improve the imbalance in the market, and on the other hand, it can promote the rapid development of the donkey industry. This study aimed to reveal significant genetic variation in the NK1 homeobox 2 gene (NKX1-2) of Dezhou donkeys and investigate the association between genotype and body size in Dezhou donkeys. Results: In this study, a SNP (g.54704925 A > G) was identified at the exon4 by high-depth resequencing of the Dezhou donkey NKX1-2 gene. The AA genotype is the dominant genotype. The g.54704925 A > G site was significantly associated with body length, thoracic girth, and hide weight (P < 0.05), while it was highly significantly associated with body height and carcass weight (P < 0.01) in Dezhou donkeys. Conclusion: Overall, the results of this study showed that the NKX1-2 gene could be a candidate gene for breeding meat-type Dezhou donkeys, and the g.54704925 A > G locus could be used as a marker locus for selection and breeding. [ABSTRACT FROM AUTHOR]

The lipid molecules and volatile organic compounds (VOCs) in milk are heavily influenced by diet. However, little is known about how roughage affects the lipid and VOC contents of donkey milk. Accordingly, in the present study, donkeys were fed corn straw (G1 group), wheat hulls (G2 group), or wheat straw (G3 group), and the lipid and VOC profiles of their milk were determined using LC–MS and GC–MS. Of the 1842 lipids identified in donkey milk, 153 were found to be differential, including glycerolipids, glycerophospholipids, and sphingolipids. The G1 group showed a greater variety and content of triacyclglycerol species than the G2 and G3 groups. Of 45 VOCs, 31 were identified as differential, including nitrogen compounds, esters, and alcohols. These VOCs were significantly increased in the G2 and G3 groups, with the greatest difference being between the G1 and G2 groups. Thus, our study demonstrates that dietary roughage changes the lipid and VOC profiles of donkey milk. [ABSTRACT FROM AUTHOR]

Simple Summary: The annual shortage of donkey hides is significant in China. Therefore, to meet the market demand, it is important to improve donkey hide production through molecular breeding. In this study, one SNP was identified in intron 1 of the LCORL gene, and polymorphism information content (PIC) was moderate in the population. The association analysis of g.112558859 A > G with body height, body length, chest circumference and hide weight was conducted and found to be significantly associated with these traits. The hide weight of donkeys with the GG genotype was 1.07 Kg heavier than those with AA genotype. This provides the foundation for breeding large donkey breeds with high hide production. Several studies have shown the association between the ligand-dependent nuclear receptor compression-like protein (LCORL) gene and body size in horses, pigs and donkeys. Based on previous studies, the LCORL gene was hypothesized to be associated with growth traits and hide weight in Dezhou donkeys. In this study, we aimed to reveal the variation of the LCORL gene in the Dezhou donkey and explore whether the gene is associated with hide weight and body size. In this study, genetic polymorphisms in the LCORL gene of the Dezhou donkey were studied using targeted sequencing technology, and single nucleotide polymorphisms (SNPs) of the LCORL gene were analyzed for association with hide weight and body size in Dezhou donkeys. The results showed that there was an SNP locus situated in intron 1 of the LCORL gene. Association analysis revealed that individuals with the GG genotype had significantly higher body height, body length, chest circumference and hide weight than those with the AA genotype (p < 0.05). Therefore, the g.112558859 A > G locus can be used as a potential candidate marker affecting body size and hide weight. This study provides the foundation for breeding high-quality donkeys with high hide yield. [ABSTRACT FROM AUTHOR]