Abstract

This study was conducted in the Layer farm of Animal production department/ College of Agriculture, University of Anbar, for the period from 20/ 7/ 2021 to 15/ 10/ 2021, to study the Effect of vitamin D₃ addition and various particle size of oyster shells to production diets in laying hens productive performance. In this study, 108 Lohman Brown laying hens, 43 weeks were distributed randomly in to nine groups, four replicates for each one three hens reared in cages (cm). The experimental treatments were as follows: T1 normal diet (control group), 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. results showed no significant differences in daily feed consumption ratio, feed conversion coefficient, egg mass and egg production in the three periods of the experiment and in average. significant improvement (P≤0.05) in average egg weight during third productive period of the experiment for the second, fifth, sixth, seventh, eighth and ninth treatments compared to the other treatments.