Effect of Limestone or Extruded Eggshell on Egg and Eggshell Quality of Laying Hens

The study aimed to determine the effect of limestone or extruded eggshells on the egg and eggshell quality of laying hens. A total of 240 and 60 eggs were collected from diets D<sub>1</sub> (limestone) and D<sub>2</sub> (extruded eggshells), respectively, with two levels of calcium source (L): L<sub>1</sub> (4% limestone or eggshells) and L<sub>2</sub> (8% limestone or eggshells) at 44, 52, 60, 68, and 72 weeks of age. These eggs were obtained from an ongoing project to measure egg quality and dry matter content. Diet D<sub>1 </sub>showed higher albumen width and height, Haugh unit, and a lower egg yolk height than D<sub>2</sub> (p<0.05). However, the percentage of albumen and yolk weight, as well as the yolk index, tended to be higher in D<sub>2</sub> than in D<sub>1</sub>. Other egg quality traits were similar between diets (p>0.05). The L<sub>2</sub> was superior to L<sub>1</sub> in both diets for egg quality traits (p<0.01), and the L<sub>2</sub> in the extruded eggshell diet performed better than L<sub>2</sub> in limestone diet. The egg, albumen, yolk, and eggshell weight, albumen width, and yolk height were increased but the eggshell strength, yolk color, albumen height, eggshell thickness, and membrane thickness were decreased with advancing the birds' age. Egg, albumen, yolk, and eggshell weight, as well as albumen width and yolk height, increased with the advancing age of the birds, whereas eggshell strength, yolk color, albumen height, eggshell thickness, and membrane thickness decreased. Egg, albumen, and eggshell with membrane weight were influenced by the diet × L interaction, while diet × age interaction affected other traits. Egg quality traits were influenced by L x A interaction, but were not affected by D x L x A interaction. The dry matter content of an egg was similar between diets, but moisture content was higher in D<sub>2</sub> than in D<sub>1</sub>. The dry matter content of albumen was influenced by diet x age interaction. Therefore, the 8% extruded eggshell appears to be the most suitable diet for improving egg and eggshell quality.