International Journal of Molecular Zoology, 2025, Vol.15, No.2, 90-100 http://animalscipublisher.com/index.php/ijmz 91 advantages. For instance, modern broilers and laying hens are both obtained through hybridization of multiple selected breeds. Hybrid breeding can not only increase weight gain rate, feed conversion rate and egg production, but also often improve economic traits such as disease resistance and environmental adaptability (Isa et al., 2020; Soliman et al., 2020). This study will explore a series of hybridization strategies for enhancing the growth rate and egg production of domestic chickens, analyze the genetic mechanism of heterosis, evaluate the effectiveness of various hybridization schemes, and discuss their impact on sustainable poultry production. This study aims to provide a reference for optimizing hybrid breeding programs to balance genetic improvement in the poultry industry with economic and practical considerations. 2 The Genetic Basis of the Main Economic Traits of Two Domestic Chickens 2.1 Genetic characteristics of growth traits The growth performance of broilers includes key indicators such as weight gain rate, body weight, pectoral muscle rate and feed conversion rate. These traits are controlled by quantitative genetics, with moderately high heritability, and there are often genetic correlations among different growth indicators. Studies have shown that the heritability of daily weight gain and feed conversion rate of broilers at 6-9 weeks of age can reach 0.3 to 0.5 or more. There is a significant negative genetic correlation between body weight and feed efficiency at different weeks of age, that is, individuals with faster growth tend to have higher feed utilization rate (Xiong et al., 2024). Multiple major genes and quantitative trait loci (QTLS) controlling growth have been identified in domestic chickens. For instance, through genome-whole association analysis, QTL regions closely related to carcass weight and pectoral muscle rate were identified on chromosomes 3 and 24 of broilers. Candidate genes included dopamine receptor D2 (DRD2), mucin receptor, etc. (Yang et al., 2021). In addition, genes that control muscle development and energy metabolism (such as IGF1, MYOD1, etc.) are also related to growth traits. Wenchang chicken is one of the high-quality local chicken breeds in China, renowned for its tender meat and moderate fat aroma. It is widely used in the breeding of high-quality broilers and the research and development of geographical indication agricultural products (Figure 1). Among domestic broilers, some QTLS have significant effects on body weight and daily gain at 4 to 10 weeks of age. The candidate genes for localization include PLCE1, LAP3, LDB2, etc., which are involved in muscle development and protein metabolism pathways (Cai et al., 2024). In broiler breeding, large-scale QTL mapping and genome-wide selection have been applied to the improvement of growth-related traits. For example, several markers screened out using the 55K SNP chip have been used for the selection of accelerating growth rate and reducing feed conversion rate (Nawaz et al., 2025). Figure 1 Picture for Wenchang chicken. (a), roosters (b), hens (Adopted from Cai et al., 2024)
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