Physico-chemical and techno-functional quality of eggs of indigenous Holli hens of Benin kept under free range and confinement systems

Indigenous chicken populations of Benin serve as an important source of supplementary income and nutrition for rural households. The current study aimed to assess the influence of rearing system on the physical, rheological, and technological characteristics of eggs from Holli hens, an indigenous breed of Benin. Therefore, 30 new laid eggs from Holli hen reared under traditional free range and 30 new laid eggs from Holli hens kept in confinement system were sampled at 32 weeks old for the different analyses. The results showed that most external egg traits, including weight (47.3 g vs. 44.4 g), length (5.14 cm vs. 4.99 cm), and height (3.68 cm vs. 3.63 cm), did not differ significantly between confinement and free-range systems. However, shell-related parameters were significantly higher in confinement eggs, including shell weight (4.36 g vs. 3.67 g), shell proportion (9.20 % vs. 8.27%), and shell thickness (0.27 mm vs. 0.23 mm). For techno-functional properties, albumen thickness was greater in confinement eggs (6.26 mm vs. 5.26 mm), while yolk diameter and yolk index remained unchanged. The Haugh unit, indicating albumen freshness, was slightly higher in free-range eggs (77.1 vs. 76.0). Remarkable differences were observed in yolk color attributes, with free-range eggs showing higher color intensity (10.2 vs. 2.0), redness (a* = 3.78 vs. –6.30), yellowness (b* = 54.0 vs. 19.3), and chroma (54.2 vs. 20.4). Correlation analysis showed strong positive associations among egg weight, shell characteristics, and albumen traits, whereas negative correlations between egg volume and Haugh unit indicated potential trade-offs between size and freshness. Overall, confinement rearing improved shell integrity and albumen thickness, whereas free-range management enhanced yolk pigmentation, reflecting diet diversity and natural foraging.