Animal Molecular Breeding, 2025, Vol.15, No.2, 60-71 http://animalscipublisher.com/index.php/amb 69 7.2 Effects of feeding conditions on growth and feather development As an important external factor affecting duck growth and feather development, feeding conditions act on epigenetic mechanisms through nutrient supply, environmental stress and management measures, thereby regulating gene expression and phenotypic expression. Changes in feed composition have a significant effect on the growth performance and feather quality of ducks. Studies have shown that methionine supplementation in feed can improve the growth rate and feather quality of ducks, especially during brooding (1 to 14 days old) and 35 days old (Zeng et al., 2015). Methionine, as a methyl donor, may regulate the expression of genes related to growth and feather development by affecting DNA methylation levels. Second, stress factors such as temperature fluctuations and transportation also have significant effects on the epigenetic status of ducks. Research has found that environmental stress can change epigenetic markers by activating stress-related signaling pathways, thereby affecting the expression of growth-related genes. In addition, drinking water management and microecological intervention are also considered important means to regulate the epigenetic status of ducks. Research points out that adding probiotics to drinking water or regulating water quality can affect the composition of the intestinal microbiota, and then affect the epigenetic regulatory mechanism through the intestinal-brain-axial pathway, promoting duck growth and feather development. 8 Commentary Summary 8.1 The importance of epigenetic regulation in duck growth and feather development The epigenetic regulatory mechanism runs through the entire growth and feather development process of ducks, and has an important impact on gene function and trait performance. Compared with traditional genetic variation, epigenetics is more dynamically plastic, which allows ducks to make adaptive adjustments in the face of environmental changes and also provides possible ways for artificial intervention. In terms of growth, DNA methylation and non-coding RNA regulate the expression of key growth genes (such as IGF1 and MSTN), which directly affects the growth rate and body composition of ducks. In terms of feather development, chromatin state and long-chain non-coding RNA determine the degree of differentiation and pigmentation of feather stem cells, shaping the rich and diverse feather morphology of ducks (Zhang et al., 2022a; Lu et al., 2024). It can be said that without epigenetic participation, it is impossible to fully explain the complex process of ducks developing from fertilized eggs to mature individuals. For ducks, their production performance (growth rate, feed conversion efficiency, carcass quality) and appearance characteristics (feather color, feather quality) are all epigenetically regulated to varying degrees. Therefore, in poultry genetic breeding and breeding management, the important role of epigenetic factors should be fully paid attention to. 8.2 Necessity and significance of deepening research The current epigenetic research on ducks is still relatively limited, far less in-depth than that of chickens and other models of birds. However, as shown in this review, some preliminary evidence has revealed the existence of epigenetic regulation of ducks and its effects on productive traits. In order to better utilize this knowledge to serve the duck raising industry, related research must be further deepened. On the one hand, it is necessary to draw an epigenetic map of the entire genome of duck, including DNA methylation groups, histone modification groups and open chromatin regions in different tissues and different periods, to find key regulatory nodes. This helps identify epigenetic markers closely related to growth and feather traits, providing new indicators for breeding. On the other hand, functional studies should be carried out to verify the causal relationship of specific epigenetic modifications on duck traits through gene editing or pharmacological means. For example, using gene editing technology to knock out specific miRNAs in duck embryos and observe their effects on muscle and feather development can clarify the function of this miRNA in epigenetic regulation. These in-depth research will deepen our understanding of duck developmental biology and also provide new tools and new ideas for cultivating high-yield and high-quality duck species. 8.3 Future development direction and cooperation initiatives The epigenetic research of ducks is in its infancy and requires multidisciplinary collaboration and new technology application. Future research directions include but are not limited to: multiomics integrated analysis: combining genome, transcriptome and epigeneticomic data to build a complex network model for the regulation of duck
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