Effect of Genotype and Storage Time on the Physical Traits of Eggs Laid by Italian Purebred Chicken Hens

A trial was carried out to profile the quality of stored eggs, at 15 °C and 75% RH until to 21 d, of 10 Italian breeds of the Veneto region with different productive purpose (egg laying purpose: Polverara nera – PO-B, Polverara bianca – PO-W, Padovana camosciata – PA-C, Padovana dorata – PA-G, Padovana argentata – PA-S; dual-purpose: Millefiori di Lonigo – MF, Pepoi – PP, Ermellinata di Rovigo – ER, Robusta Lionata – RL, Robusta Maculata – RM. All the eggs were homogeneous for the hens age and rearing system (58week-old hens, outdoor rearing). The 1-d eggs showed differences (highest vs lowest, p < 0.05) for the egg weight (ER vs PO-B), and yolk to albumen ratio (PO-B vs RL). A factorial model, breed (10 breeds) x storage time (7 d and 21 d), was used for detecting the effect of breed, storage time and interaction on the eggshell traits and internal quality (weight loss rate, albumen and yolk quality). The effect of breed was significant (highest vs lowest, p < 0.05) for shape index (MF vs ER), eggshell lightness (PO-B, PO-W, PA-C, PA-G, PA-S vs RM), and eggshell thickness (PO-W, RM vs ER). The effect of storage was significant (p < 0.05) for all the internal quality traits. According to significant (p < 0.05) effect of breed, the highest weight loss rate was shown by RM and the lowest by PA-G. The highest Haugh units were shown by PP and the lowest by PA-S. The highest yolk index was shown by RL and the lowest by PA-C. From 7 until 21 d of storage, significant (p < 0.05) changes of the egg internal quality occurred according to the breed, as the thick albumen height and the yolk height decreased in all groups, with exception of PA-C and MF, probably for changes earlier than those of the other groups, whereas the yolk diameter did not change, with exception of PP. The results indicate that the natural decline of egg quality throughout storage varies differently between the breeds and more study is needed for understanding the changes of each egg component.