Animal Molecular Breeding 2024, Vol.14, No.5, 297-306 http://animalscipublisher.com/index.php/amb 297 Review Aritcle Open Access Quantitative Trait Loci Mapping for Egg Production in Layer Hens Hongbo Liang, Jia Xuan Institute of Life Science, Jiyang College of Zhejiang A&F University, Zhuji, 311800, Zhejiang, China Corresponding author: jia.xuan@jicat.org Animal Molecular Breeding, 2024, Vol.14, No.5 doi: 10.5376/amb.2024.14.0031 Received: 21 Jul., 2024 Accepted: 30 Aug., 2024 Published: 12 Sep., 2024 Copyright © 2024 Liang and Xuan, This is an open access article published under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Preferred citation for this article: Liang H.B., and Xuan J., 2024, Quantitative trait loci mapping for egg production in layer hens, Animal Molecular Breeding, 14(5): 297-306 (doi: 10.5376/amb.2024.14.0031) Abstract Quantitative Trait Loci (QTL) mapping is a powerful tool for identifying genetic regions associated with economically important traits in poultry, such as egg production in layer hens. This study provides a comprehensive analysis of recent advancements in QTL mapping for egg production traits, including egg number, egg weight, and eggshell quality. Through the integration of high-density SNP genotyping, genome-wide association studies (GWAS), and functional genomics, key QTLs influencing these traits have been identified, offering valuable insights into the genetic architecture underlying egg production. This study highlights the potential of marker-assisted selection (MAS) and genomic selection to accelerate genetic improvement in layer hens, allowing for more precise and efficient breeding strategies. Furthermore, the integration of QTL mapping with functional genomics holds promise for uncovering the molecular mechanisms driving complex traits, such as environmental adaptability and disease resistance. Future research directions focus on refining QTL mapping through advanced sequencing technologies and expanding its application to non-traditional traits, aiming to meet the challenges of climate change and sustainable poultry production. Keywords QTL Mapping; Egg Production; Layer Hens; Marker-Assisted Selection; Genomic Selection 1 Introduction Egg production traits in layer hens are complex, influenced by various genetic and environmental factors. Key traits include egg number, egg weight, eggshell quality, and age at first egg, all of which have significant impacts on productivity and economic profitability in the poultry industry. Genetic markers and quantitative trait loci (QTL) analysis play a crucial role in understanding the genetic basis of these traits. For example, chromosomes 1, 2, 4, and Z have been identified as key QTL regions associated with egg production traits across multiple studies (Sasaki et al., 2004). Traditionally, genetic improvement in poultry breeding has been achieved through selective breeding, but the introduction of marker-assisted selection (MAS) has greatly accelerated the process. MAS uses genetic markers linked to desirable traits to select breeding individuals at an early stage, significantly reducing the generation interval and enhancing breeding efficiency. In recent years, genetic improvement techniques based on QTL mapping and genome-wide association studies (GWAS) have further refined the precision and efficiency of poultry breeding (Lien et al., 2020). This study explores the genetic architecture of egg production traits in layer hens by identifying and mapping QTL, using GWAS and high-throughput sequencing to analyze historical and current data, thereby uncovering the genetic basis of egg production traits and providing new insights for the application of marker-assisted selection and genomic tools in layer breeding to improve production performance. 2 Egg Production Traits in Layer Hens 2.1 Key traits associated with egg production Egg production in layer hens is influenced by several key traits, which are economically significant for the poultry industry. The most important traits include total egg number (EN), egg weight, and age at first egg (AFE). Total egg number represents the number of eggs laid over a specific period, making it a crucial measure of production performance and a common selection criterion for breeding. Egg weight affects the market value of the eggs, as heavier eggs are generally more desirable for consumers and thus, impact the pricing (Liu et al., 2019).
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