Abstract
BACKGROUND AND AIM: Local Indonesian chickens possess valuable dual-purpose traits for both meat and egg production, but exhibit lower productivity compared to commercial breeds. Genetic enhancement through selective crossbreeding and molecular marker analysis, such as growth hormone (GH) gene polymorphism, offers a strategy to improve performance traits. This study aimed to characterize quantitative traits and analyze GH gene polymorphism in crossbred chickens resulting from mating Arab chickens with five indigenous breeds. MATERIALS AND METHODS: Five local breeds, Kampung Super, Sentul, Bangkok, Kampung, and Merawang, were each crossed with Arabian chickens using a 1:7 male-to-female ratio. Phenotypic evaluations included body weight (BW), weight gain, and 18 morphometric traits measured at various ages. Egg traits were monitored for 4 weeks. GH gene polymorphism was identified in 500 crossbred individuals using polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) with the AluI enzyme restriction. Data were analyzed through a one-way analysis of variance and General Linear Models to determine phenotypic and genotypic associations. RESULTS: Significant differences (p < 0.05) in BW, BW gain, morphometric size, and egg traits were observed among parental and crossbred groups. Kampung Super × Arab chickens showed the highest performance across growth and reproductive metrics. The highest weight gain occurred between 2 and 3 months of age. Back height emerged as a key morphometric indicator of growth differences. PCR-RFLP revealed GH gene polymorphism with three genotypes: (+/+), (+/-), and (-/-). The (+/+) genotype had a significant (p < 0.05) positive impact on BW, weight gain, and back height. All populations were in Hardy-Weinberg equilibrium, and polymorphic information content values (~0.437) indicated moderate genetic diversity. CONCLUSION: This study is the first comprehensive integration of morphometric, phenotypic, and GH genotypic data in Indonesian crossbred chickens. The findings support the implementation of marker-assisted selection to enhance growth traits in breeding programs. Future work should assess multi-generational effects and integrate additional molecular markers to optimize breeding strategies across tropical poultry systems.