The effect of different dietary electrolyte balances on eggshell quality in laying hens

This study was carried out to determine the effects of different dietary electrolyte balances (DEB) on eggshell quality, egg weight, bone ash, litter dry matter and on some blood parameters in laying hens. A total of 216 Lohmann-Brown layer hens were used in this experiment, and birds were randomly separated into 4 equal groups, each group containing 54 hens. The DEB of the control group was 170 rnEq/kg, and in assay groups, DEBs were adjusted to 80 mEq/kg (group 1) with NH4Cl, 256 rnEq/kg (group 2) with NaHCO3 and to 330 mEq/kg (group 3) with NaHCO3 and KHCO3. The experiment lasted 8 weeks. Hen day egg production. eggshell quality (shell ash, thickness, strength, cracked egg ratio), egg weight. percentages of litter dry matter and bone ash, glucose and mineral concentrations and acid-base equilibrium related parameters (blood pH, HCO3- concentrations. pCO(2), pO(2),) were determined. Average egg weight and final litter dry matter percentage were significantly higher in the group 2 than it) the other groups (P < 0.001). In the g-roup 2, eggshell thickness and strength significantly increased compared to the group 1 (P < 0.05), and the cracked egg ratio significantly decreased compared to the groups I and 3 (P percentage was also significantly enhanced compared < 0.01). The tibia as to the control group (P < 0.05). Moreover, moderate (,group 2) or high (group 3) DEB induced significant decreases of chloride concentrations during the 4 first weeks, and increases of HCO3- concentrations (P < 0.001). Blood pH values were significantly higher in the group 3 than in the group 1 (P < 0.001). These results indicate that dietary alkaline supplementation achieves a partial correction of the lay-induced metabolic acidosis, and that negative effects on eggshell quality were observed when chloride excess was associated with changes in electrolyte balance. Consequently, a moderate DEB (256 mEq/kg) can improve eggshell quality and acid-base equilibrium in laying hens.