Comparison of Egg Quality Characteristics of Three Yunnan Local Chicken Breeds and Commercial Laying Hens

Purpose To systematically compare the egg quality characteristics of three local chicken breeds in Yunnan Province (Yanjin black-bone, Nixi, and Lanping silky chickens) with mainstream commercial laying hens (Hy-Line Brown and ISA Brown), and to objectively evaluate their quality differences and germplasm advantages.

Methods A total of 150 healthy laying hens at the peak of egg production (at 30 weeks of age) from the same hatching batch were selected (30 birds per breed). Under uniform feeding and management conditions, 300 fresh eggs (60 per group) were collected to measure 10 quantitative parameters, including egg weight, eggshell thickness, yolk ratio, yolk color, and Haugh unit. Inter-group differences were analyzed using one-way ANOVA. Trait associations were revealed by Pearson correlation analysis, and a comprehensive evaluation model was constructed based on principal component analysis (PCA).

Results The three Yunnan local breeds exhibited significantly higher yolk ratios (0.29-0.31 vs. 0.24-0.25) and yolk color grades (9.00-10.00 vs. 6.34-7.84) than the two commercial layers (P<0.05). The Haugh units of all tested groups ranged from 73.22 to 77.36, meeting the national standard for AA-grade fresh eggs (≥72). Notably, Yanjin black-bone chicken showed the highest yolk ratio (0.31) and the greatest eggshell strength (3.62 kg/cm²) among the local breeds. Correlation analysis indicated that exterior physical parameters (e.g., egg weight and eggshell thickness) were extremely significantly and negatively correlated with core internal sensory and nutritional traits (e.g., yolk ratio and yolk color) (P<0.01). The PCA extracted two principal components with a cumulative variance contribution rate of 65.600%. Based on the comprehensive PCA scores, the overall egg quality ranked as follows: Yanjin black-bone chicken>Lanping silky chicken>Nixi chicken>ISA Brown>Hy-Line Brown.

Conclusion Despite having relatively smaller egg weight, the three Yunnan local chicken breeds (Yanjin black-bone, Nixi, and Lanping silky chickens) possess a physiological characteristic of directionally and efficiently enriching reproductive nutrients into the yolk during follicular development. Their internal sensory traits and comprehensive egg quality are significantly superior to those of the commercial laying hens under long-term intensive directional selection, indicating a high potential for the development of specialty premium eggs.