Document Type : Research Paper
Authors
1 Department of Animal Science, Razi University, Kermanshah, Iran
2 Department of Animal Science, Faculty of Agriculture and Natural Resources, Razi University, Kermanshah, Iran
3 Monogastric Research Centre, School of Agriculture and Environment, Massey University, New Zealand.
Abstract
The aim of this study was to evaluate the effect of calcium levels and particle size of limestone on performance, egg quality, gizzard Ca, and apparent and true ileal Ca digestibility coefficient in commercial laying hens. The experiment was conducted in a completely randomized factorial design (3×2) with three calcium levels (80%, 100%, and 120% of strain requirements; 3.27%, 4.09%, and 4.9%, respectively) and two particle sizes: fine (GMD= 406 µm) and coarse (GMD= 2766 µm) from 57-68 weeks in Lohmann (LSL lite) laying hens. Apparent and true ileal calcium digestibility coefficients increased with increasing limestone particle size (P < 0.01). The true calcium digestibility of fine limestone at 80%, 100%, and 120% of requirements was 0.494, 0.458, and 0.495, respectively, while for coarse limestone, it was 0.514, 0.644, and 0.698, respectively. The results of this experiment indicated that by increasing the particle size of calcium carbonate (from 406 to 2766 μm), the true calcium digestibility coefficients (0.482 vs. 0.619) and total tract retention increased, which was accompanied by an improvement in eggshell weight. A notable point in the results of this experiment was the lack of effect of calcium level on calcium digestibility coefficients and laying hen performance. Therefore, if in the laying hen industry, the desired eggshell thickness is achieved with 80% of the strain requirement, the calcium level in commercial diets can be reduced.
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