The Effects of Dietary Calcium Sources and Vitamin D3 on Egg Quality and Performance in Laying Hens

This experiment was designed to evaluate the effects of different sources of calcium at different rates and cholecalciferol (Vitamin D3) on the performance and egg quality of Hy-line W-36 Laying hens. In this study a total of 648 hens were managed in a completely randomized design using a factorial arrangement of 3 × 3 × 2 treatments, with three calcium sources (oyster shell, OS; ground limestone, GLI; fine limestone, FLI) and three different rates (70:30, 30:70, 50:50) and two levels of vitamin D3 (3300 and 5000 IU/kg diet). At 33-wk of age, hens received 18 treatments (3 replicates per treatment) until 45 wk. The results showed that egg weight (g), egg production (%), egg mass (g), feed intake (g), feed conversion ratio and egg quality traits which involve egg gravity, yolk index, shell weight (g), and Haugh unit were not effected by calcium sources and different levels of vitamin D3. The high level of vitamin D3, resulted in an increase of eggshell thickness, ash and calcium percentage of eggshell (P < 0.05). Moreover, replacement of 50-70% FLI or GLI with OS improved eggshell quality (P < 0.05). There was a significant (P < 0.05) interaction be-tween Ca sources and vitamin D3 level on eggshell quality. Hens fed with diets containing OS/GLI at 70:30 and vitamin D3 at 5000 IU/kg showed the highest values for eggshell thickness, calcium and ash (P < 0.05). These results clearly indicated that supplying calcium sources, with at least 1 / 2 OS (large particle) with or without high level of D3, can significantly improve eggshell quality without adverse effects on the laying performance in first cycle of the laying period.