Abstract
A study was conducted to evaluate the effect of 25-hydroxyvitamin D3 (25-OHD) with different levels of vitamin D3 (VD3) during the rearing period (1–20 weeks) on laying hen performance, bone quality, and eggshell quality. A total of four hundred 1-day-old Lohman pullets were randomly allotted into a 2 × 2 factorial design with 2 levels of dietary VD3 (300 and 2800 IU/kg) and 2 levels of dietary 25-OHD (0 and 56 μg/kg). Each treatment had five replicates of 20 hens each. Increasing the dietary VD3 level (2800 vs. 300 IU/kg) tended to increase body weight uniformity (0.05 < p < 0.1) at 8 weeks. Dietary VD3 levels and supplementation of 25-OHD during the growing period (1–20 weeks) did not improve the laying performance and eggshell quality (eggshell strength, eggshell thickness, and eggshell relative weight) during the laying period (p > 0.05). Compared with the 300 IU/kg VD3 group, the 2800 IU/kg VD3 group showed higher serum calcium concentration and keel length at 10 weeks (p < 0.05). The addition of 25-OHD significantly increased serum calcium and 25-OHD concentration at 10 and 20 weeks and keel calcified rate at 20 weeks (p < 0.05). Increasing dietary VD3 level (2800 vs. 300 IU/kg) increased tibia ash and phosphorus content at 10 weeks, tibia strength at 72 weeks (p < 0.05), and tended to increase tibia ash content at 72 weeks, tibia calcium content and tibia strength at 20 weeks (0.05 < p < 0.1). Dietary supplementation with 25-OHD increased tibia ash content at 10 weeks, tibia calcium content and tibia strength at 20 weeks (p < 0.05), and tended to increase tibia ash content at 72 weeks (0.05 < p < 0.1). Overall, the results gathered in this study indicate that dietary supplementation of high levels of VD3 and 25-OHD during the growing period improved the tibia quality of laying hens during the early and later laying period, but had no effect on laying performance and eggshell quality during the laying period.
Highlights
There was a significant interaction for body weight uniformity (BWU) at 8 weeks between dietary vitamin D3 (VD3) level and 25-OHD (p < 0.05), and increasing dietary
In the current study, we found that dietary supplementation with 25-OHD had no effect on body weight, average daily feed intake (ADFI), and shank length of pullets; this is in agreement with a recent research indicating that dietary supplementation of 69 μg/kg 25-OHD did not affect the growth performance of pullets compared with 2760 IU/kg VD3 treatment [12]
We found that dietary VD3 levels and 25-OHD at growth period had no effect on eggshell quality
Summary
Bone quality is closely related with egg production and eggshell quality [1]. Studies have shown that hen keel bone damage may be painful to birds and affect their production [4]. A recent study showed that pullet fed low calcium and phosphorus diet had lower relative keel bone weight and ash content, and tibia ash content; and serum pyridinoline (a bone resorption marker) was significantly increased [6]. When bone resorption failed to maintain normal levels of calcium in the blood, birds developed hypocalcemia and secreted high levels of serum parathyroid hormone (PTH) [7]. Within the normal physiological range, high serum calcium levels are necessary to maintain good bone quality in pullets
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