Dietary supplementation with sodium bicarbonate improves calcium absorption and eggshell quality of laying hens...

The advantage of supplemental sodium bicarbonate (NaHCO3) on eggshell quality in laying hens changes with age. Besides increasing calcium (Ca) secretion in the eggshell gland, it may improve Ca absorption in the intestine or kidney. Hy-Line Brown layers (n = 384), 25 weeks of age, were allocated to two treatment groups in two experiments, each of which included 4 replicates of 24 hens. Hens were fed a basal diet (control) or the basal diet containing 3 g NaHCO3 g/kg for 50 or 20 weeks in Experiment 1 or 2, respectively. A 24-h continuous lighting regimen was used to allow hens to consume the dietary supplements during the period of active eggshell formation. In Experiment 1, particularly from 25 to 50 weeks of age, and in Experiment 2, NaHCO3 supplementation favoured hen-d egg production at the expense of lower egg weight. The increased eggshell thickness should have nothing to do with the additional eggshell formation, because of the unchanged egg mass and daily eggshell calcification. At 35 weeks of age in both experiments, NaHCO3 supplementation increased duodenal expression of calbindin-d28k (CaBP-D28k) protein, contributing to higher Ca retention and balance. From 50 to 75 weeks of age in Experiment 1, the hens had little response to NaHCO3 supplementation and showed a negative trend on eggshell thickness and strength. It is concluded that dietary supplementation with 3 g NaHCO3 g/kg improves Ca absorption and eggshell quality of laying hens during the peak but not late production period, with the introduction of continuous lighting.