Research note: Genetic parameters estimation of egg quality traits in Beijing-You chickens

The Beijing-You chicken, a dual-purpose breed with a long-standing history and robust adaptability, is the only indigenous chicken breed in Beijing, China. Evaluating its egg quality traits is critical for conserving genetic resources and guiding breeding programs. Phenotypic data from two generations of Beijing-You chickens were collected, including 15 traits: egg weight (EWT), eggshell strength (ESS), albumen height (AH), yolk color (YC), yolk weight (YW), eggshell weight (ESW), eggshell-to-egg weight ratio (ESWR), albumen weight (AW), egg shape index (ESI), Haugh unit (HU), albumen-to-egg weight ratio (AWR), yolk-to-albumen weight ratio (YAWR), yolk-to-egg weight ratio (YWR), eggshell translucency (EST), and eggshell freckles (ESF). Variance components, genetic correlations, and phenotypic correlations were analyzed using the Asreml R toolkit (v 4.2.0.332) with the average information (AI) algorithm. Results revealed heritability estimates ranging from 0.02 (EST) to 0.61 (AW), with most traits showing moderate to high heritability. Notably, the value of YWR (30.44 %) and ESS (4.18 kg/cm²) outperformed those reported for high-yielding chicken breeds. High genetic correlations included a high positive correlation between EWT and ESW (r_G = 0.568) and strong negative correlations between EWT and ESS (r_G = -0.541) and between EWT and ESWR (r_G = -0.535). ESS and ESWR exhibited a high positive genetic correlation (r_G = 0.844), while YC and AH showed a significant negative correlation (r_G = -0.662). This study presents the first comprehensive characterization of genetic parameters underlying egg quality traits in Beijing-You chickens, especially for the facts of higher yolk-to-egg weight ratios and a negative genetic correlation between eggshell strength and egg weight, providing essential genetic insights for precision breeding strategies in native poultry populations.