Abstract: To elucidate the dynamic changes in egg quality characteristics of the Baicheng-You chicken, a distinctive local breed, this study systematically evaluated the laying performance and 13 egg quality parameters of 771 hens aged 21 to 53 weeks. Multiple nonlinear models, including YangNing, Segmented, and Cubic, were employed to fit the egg production performance curves. Principal component analysis (PCA) was used to establish a comprehensive egg quality evaluation system, and the correlation between age at first egg (AFE) and egg quality at different stages were analyzed. The results indicated that all egg quality parameters, except shell thickness, exhibited significant stage-specific variations (P < 0.05). Nutritional indicators such as egg mass, yolk mass, and yolk ratio increased significantly with age, whereas Haugh unit values declined. Model fitting revealed that YangNing, Segmented, and Cubic models were the optimal models for average egg production, feed conversion ratio, and average egg mass, respectively (R2 ≥ 0.966). The correlation between AFE and egg quality displayed stage-specific patterns, with 145–165 days of age identified as the optimal window for first egg laying. PCA demonstrated that eggs laid during the late laying period (48 weeks) received the highest comprehensive egg quality score (0.912 ± 0.660). Our comprehensive evaluation model provides theoretical and methodological support for quality standard formulation, graded production, and value-added utilization of Baicheng-You chicken eggs.

Key words: Baicheng-You chicken; egg quality; principal component analysis; curve fitting; dynamic evaluation