Abstract

This study was conducted in the poultry farm belong to Department of Animal Production at College of Agriculture, University of Anbar, from 20/7/2021 to 15/10/2021, to show the role of vitamin D3 and multi particle size of oyster shells to providing the needed calcium for laying hens in order to manufacture the eggshell throughout the hours of the day and its impact on shell quality and bone health.one hundred-eight Lohman Brown laying hens, 43 weeks of age, were distributed randomly to nine treatments, four replicates for each treatment and three hens for each replicate. The experimental treatments were as follows: T1/ control diet without any additives, T2/ calcium source 50% limestone + 50% oyster shell size less than 1 mm + vitamin D₃ 4000 IU kg^-1, T3/ calcium source 50% limestone +50% oyster shell size 1-2 mm + vitamin D₃ 4000 IU kg^-1, T4/ calcium source 50% limestone + 50% oyster shell size 2-3 mm + vitamin D₃ 4000 IU kg^-1, T5/ calcium source 50% Limestone + 50% oyster shell size 3–5 mm + Vitamin D₃ 4000 IU kg^-1, T6/ Calcium source 50% limestone + 50% oyster shell size less than 1 mm + Vitamin D₃ 8000 IU kg^-1, T7 / Calcium source 50% limestone + 50% oyster shell 1-2 mm +Vitamin D₃ 8000 IU kg^-1, T8 Calcium source 50% limestone + 50% oyster shell 2-3 mm + Vitamin D₃ 8000 IU kg^-1, T9/ Calcium source 50% limestone +50% oyster shell size 3-5mm + Vitamin D₃ 8000 IU kg^-1. The results showed a significant increase (P≤0.05) in levels of calcium in blood plasma for fifth, sixth, seventh, eighth and ninth treatments. The results indicated a Significant increase (P≤0.05) in level of vitamin D₃ in blood plasma for the sixth, seventh, eighth and ninth treatments. The results showed a significant increase (P≤0.05) in tibia bone breaking strength and Calcium content in tibia bone for the sixth, seventh, eighth and ninth treatments. The results of eggshell breaking force trait indicated significant increase (P≤0.05) for fourth, fifth, sixth, seventh, eighth and ninth treatments.