## 3 Results and Discussion
### Eggshell Mechanical and Quality Traits
\begin{table}
\begin{tabular}{c c c c c c c c} \hline \multicolumn{4}{c}{**Factors**} & \multicolumn{4}{c}{**Response Variables**} \\ \hline
**D \({}^{1}\)** & **H \({}^{2}\) (w)** & **Fmax \({}^{3}\) (N)** & **\% Def \({}^{4}\)** & **Ea \({}^{5}\) (N \(\times\) mm)** & **\% Shell \({}^{6}\)** & **T \({}^{7}\) (mm)** \\ \hline C & & 47.6 & 0.65 & 9 & 10.1 & 0.37 & a,b \\ CAM10 & & 48.4 & 0.68 & 9 & 10.2 & 0.38 & a \\ CAM20 & & 47.6 & 0.68 & 9 & 9.9 & 0.36 & b \\  & 24 & 50.5 & 0.74 & 10 & 10.3 & a & 0.37 & \\  & 43 & 45.2 & 0.60 & 8 & 9.8 & b & 0.37 & \\ C & 24 & 53.2 & a & 0.75 & a & 11 & a & 10.5 & 0.38 & \\  & 43 & 42.3 & b & 0.55 & c & 7 & 0 & 9.7 & 0.36 & \\ CAM10 & 24 & 50.6 & a & 0.73 & a,b & 10 & a,b & 10.4 & 0.37 & \\  & 43 & 46.3 & a,b & 0.62 & b,c & 8 & b,c & 10.0 & 0.38 & \\ CAM20 & 24 & 48.2 & a,b & 0.73 & a,b & 9 & a,b & 10.1 & 0.36 & \\  & 43 & 46.9 & a,b & 0.62 & b,c & 8 & b,c & 9.7 & 0.37 & \\ Pooled SEM & 2.235 & & 0.006 & 0.252 & & 0.222 & 0.0003 & \\ ANOVA & & & & & \(p\) & & & \\ \hline H & \textless{}0.001 & \textless{}0.001 & \textless{}0.001 & \textless{}0.001 & \textless{}0.001 & 0.931 & \\ D & 0.875 & 0.408 & 0.845 & 0.118 & 0.043 & \\ H \(\times\) D & 0.033 & 0.048 & 0.026 & 0.320 & 0.093 & \\ \hline \end{tabular} \({}^{\text{a}}\)\({}^{\text{c}}\) Statistically significant differences in columns (\(p\leq 0.05\)) are indicated by different superscripts; \({}^{1}\) D = diet; \({}^{2}\) H = Hen age expressed in weeks; \({}^{3}\) Fmax = measured Rupture Force; \({}^{4}\) %Def = Specific Deformation = \(100\times\) measured Deformation at rupture / egg length; \({}^{5}\) Ea = Rupture Energy = Fmax \(\times\) measured Deformation at rupture / 2; \({}^{6}\) % shell = \(100\times\) eggshell weight / total egg weight; \({}^{7}\) T = Shell Thickness = \(10\times\) eggshell weight /Surface x 2.3) where Surface is calculated as in [PERSON] 2005 [43].  
\end{table} 
Table 6: Effect of hen age and different amelina cake level in the diet on compression test response variables (Rupture Force, Specific deformation, and Rupture Energy), and shell traits (shell percentage and thickness) of eggs with shape index 78.5–79.5. Control diet (C) and amelina diets (CAM10 and CAM20). did not affect these shell traits. [PERSON] et al. (2012) [49] reported a significant difference in shell thickness between the two amelina groups; amelina 10% showed significantly lower shell thickness than amelina 5%. Moreover, the presence of amelina cake at 5 and 10% significantly increased the shell resistance to fracture of both amelina groups. Our results are in line with this last author, taking into account, however, the differences of the two studies in terms of hen genotype, age, and amelina percentage in the diet. Bioactive molecules (phenols, tocopherols, and flavonoids) contained in amelina cake [60] could be involved in protecting eggshell as hens become older. Synthetic antioxidants of vitamin E [61] and flavonoids supplements [62; 63] already demonstrated, in fact, a positive effect on eggshell of heat-stressed or aged hens. Research should, therefore, be carried out and widened to understand better how amino acids, minerals, micronutrients, and bioactive molecules contained in amelina cake relate to the organic components of true shell and shell membrane, to shell composition, to calcium metabolism and availability, as well as to shell ultrastructure.