Laying hen biodiversity: a study on the effect of age on the yield performance and quality of eggs produced by two Italian purebred hens

Yield performance and external and internal quality traits of eggs laid by two Italian purebreds, Ermellinata di Rovigo (ER) and Pepoi (PP) were studied at 36 and 50 weeks of age. Daily egg production and egg traits were evaluated by a factorial model (2 x 2) with genotype and age as main effects and their interaction. The daily laying rate was similar between the breeds and the hen-day egg mass was higher (p<0.01) for ER than for PP. The ER eggs differed (p<0.01) from PP eggs with higher egg weight, yolk and albumen weight, and a more coloured eggshell with lower L, higher a* and b*, and lower eggshell thickness. PP showed more (p<0.05) inclusion of albumen than yolk in comparison to ER. With increased hen age, egg weight, eggshell lenght, width, lightness and thickness increased (p<0.01), whereas shape index and a* and b* did not change. Throughout the laying period, the eggs were classified as small (PP) and medium size (ER). With increased hen age, PP eggs were more spherical, ER eggs were more ovoid; yolk and albumen weight increased (p<0.01) in ER, whereas yolk and eggshell weight increased (p<0.01) in PP. The yolk:albumen ratio increased (p<0.01) along with hen‘s age and the Haugh Units and egg inclusions decreased (p<0.01). The ER and PP eggs differed for many egg external traits, which allow to distinguish the eggs by weight, shape, and eggshell colour and for the eggshell thickness and the albumen traits.