Use of extruded eggshell as a calcium source substituting limestone or oyster shell in the diet of laying hens

The nutritional values of limestone, oyster shell and extruded eggshells were evaluated using different methods. In total, 120 ready-to-lay pullets, 18-week-old ISA Brown were distributed into six dietary groups, namely D₁ (4% limestone), D₂ (8% limestone), D₃ (4% oyster shell), D₄ (8% oyster shell), D₅ (4% eggshell) and D₆ (8% eggshell), to assess the effect of calcium sources on egg production, egg quality, dry matter and cholesterol content of the egg. Kitchen-extruded eggshell contained 98.52, 4.24, 29.75 and 14.82% DM, CP, Ca and P, whereas hatchery-extruded eggshell contained 99.20, 13.80, 25.53 and 13.87% DM, CP, Ca and P, respectively. Limestone and Oyster shells contained 99.60 and 99.51% DM, and 37.12 and 35.20% Ca, respectively. Body weight, egg, hen day and egg mass production, and FCR did not differ among diets (p > .05). Egg production tended to increase with the increase of hen-housed egg production (p < .001) in D₆ , followed by D₂ , D₅ , D₃ , D₄ and D₁ , respectively. The lowest production cost and the highest net profit were observed in D₆ , followed by D₂ , D₄ , D₅ , D₁ and D₃ , respectively. Diet with 8% Ca sources performed better than the diets with 4% Ca sources in terms of egg quality and dry matter content, where D₆ was comparable to D₂ or D₄ . The weight of egg, albumen, yolk, eggshell, dry yolk and yolk-albumen ratio increased, while dry albumen and eggshell weight, eggshell strength and thickness, Haugh unit, yolk index and egg-specific gravity decreased with the increase in bird's age. The cholesterol content of yolk was statistically similar among diets. Therefore, no adverse effect of calcium sources on the production of laying hen was observed. Of these, extruded eggshell especially the 8% extruded eggshell may be beneficial to use in the diet of laying hen for producing a quality, safe and profitable egg.