Effect of different vitamin D sources and calcium levels in the diet of layers in the second laying cycle

Gr Do Nascimento,Jc Fanhani,Afqm Guerra,Mfz Ferreira,Ae Murakami,Ic Ospinas-Rojas

doi:10.1590/1516-635x160237-42

Gr Do Nascimento, Jc Fanhani + Show 4 more

Open Access

https://doi.org/10.1590/1516-635x160237-42

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Abstract

This study evaluated the effects of different sources of vitamin D and calcium levels on performance, egg quality and bone strength of hens in the second production cycle. A total of 384 Hy-Line W36 birds with 80 weeks of age were used, alloted into 3 x 4 factorial design (sources of vitamin D: cholecalciferol; 25(OH)D3 and 1.25(OH)2D3 x calcium levels: 2.85, 3.65; 4.45 and 5.25%) with four replicates and eight birds each. The performance was evaluated for three cycles of 28 days each, egg quality was evaluated in the last four days of each cycle and bone strength on the last day of the experimental period. There was no interaction (p > 0.05) between the different sources of vitamin D and calcium levels in all parameters evaluated. There was a quadratic effect (p < 0.05) of calcium levels in egg production and feed conversion (kg/kg and kg/dz), with better results at levels of 4.12%, 4.09% and 4.14%, respectively. Calcium levels had no effect (p > 0.05) in the egg weight and Haugh unit, but there was a linear increase (p < 0.05) in the percentage and eggshell thickness, in specific gravity and bone strength. The different sources of vitamin D influenced (p < 0.05) the egg production rate, feed conversion, egg weight and Haugh unit. Thus, the results of this study suggest that the recommended calcium level for laying on second cycle is between 4.09% and 4.14% and that the metabolites cholecalciferol and 25(OH)D3 improved the performance and egg quality. Regarding bone strength was improved as the calcium levels were increased in diets.

Highlights

During the second laying cycle, after forced molting, layers restore their calcium absorption levels, with resulting eggshell quality improvement
Blood calcium is rapidly mobilized, thereby reducing its levels. This stimulates the secretion of the parathyroid hormone (PTH), which promotes bone resorption to reestablish calcium homeostasis (Pelícia et al 2009)
Considering the egg production and feed conversion ratio results obtained in the present study, 4.09 and 4.14% dietary calcium levels are recommended for layers in their second laying cycle, respectively

Summary

Introduction

During the second laying cycle, after forced molting, layers restore their calcium absorption levels, with resulting eggshell quality improvement. This effect is independent of egg size, and eggshell quality worsens as birds age (Albano Jr et al, 2000). During the second laying cycle, commercial layers present high egg loss due to poor eggshell quality and weak bones due to calcium mobilization. Their calcium and vitamin D requirements need to be updated to improve egg quality and the productivity of the egg industry. The high rates of bone resorption during lay result in bone weakness in layers by the end of their production cycle (Whitehead, 2004)

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