Animal Molecular Breeding 2024, Vol.14, No.5, 318-325 http://animalscipublisher.com/index.php/amb 321 In summary, the identification and functional analysis of key genes, along with the understanding of their regulation during different growth stages, provide valuable insights into the molecular mechanisms underlying muscle development in broilers. These findings can be utilized to enhance muscle growth and improve the overall productivity of broiler chickens. 5 Case Study 5.1 Background of the case study Broiler chickens are selectively bred for rapid growth and high feed efficiency, making them a crucial component of the poultry industry (Tallentire et al., 2016). Understanding the genetic mechanisms underlying muscle development in broilers can lead to improved breeding strategies and enhanced meat production (Buzała and Janicki, 2016). This case study focuses on identifying key genes involved in muscle development through gene expression analysis in broilers, leveraging various methodologies and findings from recent research. 5.2 Gene expression analysis The methodologies employed in the gene expression analysis of broiler muscle development are diverse and robust. One common approach is the use of RNA sequencing (RNA-seq) to compare transcriptomes at different developmental stages or between different phenotypes (Kanakachari et al., 2021). For instance, RNA-seq was used to study the transcriptome of breast muscle in male Jinghai yellow chickens at different ages, identifying differentially expressed genes (DEGs) and enriched biological processes and pathways. Similarly, microarray analysis has been utilized to investigate global RNA expression in breast muscle, identifying differentially expressed genes associated with feed efficiency (Bottje et al., 2012). In another study, transcriptome sequencing was applied to compare the leg muscles of fast- and slow-growing chicken embryos, identifying differentially expressed circRNAs and constructing circRNA-miRNA networks (Zhang et al., 2022). Additionally, large-scale transcriptome sequencing was performed on approximately 400 Tiannong partridge chickens to detect candidate genes for breast muscle weight and intramuscular fat content, using linear mixed models and regularized linear regression models. 5.3 Results and implications for broiler muscle development The results from these studies have provided significant insights into the genetic basis of muscle development in broilers. For example, the study on male Jinghai yellow chickens identified 4608 DEGs across different age groups, with key genes such asSNCG, MYH1A, andARHGDIBbeing co-differentially expressed (Zhang et al., 2021a). These genes are involved in various biological processes and pathways related to muscle growth and development. Another study focusing on feed efficiency found that high feed efficiency in broilers is associated with the upregulation of genes involved in anabolic processes and the downregulation of genes related to muscle fiber development, muscle function, and cytoskeletal organization (Bottje et al., 2011). This suggests that selective breeding for feed efficiency may inadvertently affect muscle development pathways. The transcriptome analysis of fast- and slow-growing chicken embryos revealed significant circRNAs and their potential regulatory roles in skeletal muscle development (Lei et al., 2022). Key circRNAs such as novel_circ_0004547 and novel_circ_0003578 were identified, along with their associated miRNA pairs, providing new targets for genetic improvement. Furthermore, the large-scale transcriptome sequencing study identified 43 candidate genes associated with breast muscle weight and several genes related to intramuscular fat content. These genes are involved in muscle development, contraction, and lipid metabolism, offering valuable targets for genetic improvement programs (Kang et al., 2021). In conclusion, the gene expression analyses conducted in these studies have identified numerous key genes and pathways involved in muscle development in broilers. These findings have significant implications for the poultry industry, providing potential targets for selective breeding and genetic improvement to enhance muscle growth and feed efficiency in broilers.
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