Substitution of inorganic with organic forms of minerals as an alternative way to reduce their concentrations in diet and excretion in laying hens

This experiment was conducted to evaluate the effect of zinc, manganese and copper sources (inorganic vs. organic) in the diet on laying performance and eggshell quality characteristics. One hundred and eighty Hy-Line W-36 layers at 38 wk of age were allocated to 36 layer cages of 5 hens each. Each six cages were randomly assigned to one of the six experimental diets fed from 38 to 53 weeks of age. In three experimental treatments the basal diet was supplemented with 65-75-7 or 65-75-7 or 40-40-7 mg/kg of Zn, Mn and Cu, respectively from their oxide or sulfate sources. Three other groups were fed diets supplemented with 20-20-3.5 or 40-40-7.5 or 60-60-10.5 mg/kg of organic forms of Zn, Mn and Cu, respectively. Dietary treatments significantly did affect feed intake (P<;0.001), feed conversion ratio (P<;0.001) and percentage of broken eggs (P<;0.05). Substitution of Zn and Mn oxides (65 and 75mg kg^-1, respectively) with equal amounts of their sulfate forms significantly improved feed intake, feed conversion ratio, percentage of broken eggs and Haugh Unit (P<;0.05). In addition, laying hens maintained their performance when substitution of Zn and Mn oxides and Cu sulfate (65, 75 and 7mgkg^-1, respectively) reduced up to 20, 20 and 3.5 mgkg^-1 by amino acid complexes of the microelements. The results showed that a corn-soybean diet supplemented with the organic forms of Zn, Mn and Cu at a dosage 50 to 75% lower than NRC recommendation is sufficient to maintain laying performance and can improve eggshell and albumen qualities of the eggs in lying hens.