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Pakistan Journal of Biological Sciences
Year: 2005  |  Volume: 8  |  Issue: 9  |  Page No.: 1311 - 1317

Supplementation of a Corn-soybean Meal Diet with Manganese and Zinc Improves Eggshell Quality in Laying Hens

A. Zamani, H.R. Rahmani and J. Pourreza    

Abstract: An experiment was conducted to evaluate the effects of supplementing the diet of laying hens with a combination of Zn and Mn on eggshell quality. Six hundred and forty white leghorn laying hens, strain Hy-Line W36 were divided into two groups according to age (28 and 44 week old). Each group then was divided into 64 and five birds per group (totally 128 groups). In both groups every four cages were assigned to one of the 16 experimental diets. Sixteen experimental diets included a corn-soybean basal diet containing 50 mg kg-1 Zn and 30 mg kg-1 Mn supplemented with 0-0, 0-30, 0-60, 0-90, 50-0, 50-30, 50-60, 50-90, 100-0, 100-30, 100-60, 100-90, 150-0, 150-30, 150-60 and 150-90 mg kg-1 of Zn and Mn, respectively. Addition of Zn increased eggshell thickness, concentration of Ca in eggshell and eggshell index and decreased concentration of P in eggshell significantly (p<0.05) and did not affect the following measures of eggshell quality: percentage, stiffness, elastic modulus, breaking strength and fracture toughness of eggshell and egg weight. In contrast addition of Mn increased percentage, stiffness, elastic modulus, breaking strength and fracture toughness of eggshell significantly (p<0.05), but did not affect the following measures of eggshell quality: Concentration of P and Ca, index and thickness of eggshell and egg weight. Addition of Zn and Mn in combination increased percentage, index (shell weight per unit surface area), stiffness, elastic modulus, breaking strength, thickness, fracture toughness and concentration of Ca in eggshell and decreased concentration of P in eggshell and did not affect egg weight. In older hens there was a significantly increase in egg weight, breaking strength, elastic modulus, stiffness and fracture toughness of eggshell and significantly (p<0.05) decrease in thickness, percentage and index of eggshell without any effect on concentration of P and Ca in eggshell.

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