Relative bioavailability of 25-hydroxyvitamin D3 compared to vitamin D3 for laying performance and egg quality in laying hens from 41 to 48 weeks of age

Abstract

Currently, the primary supplemental forms of vitamin D (VD) for laying hens’ diets are traditional Vitamin D₃ (VD₃) and its intermediate metabolite, 25-hydroxyvitamin D₃ (25-OHD). However, the application effect of 25-OHD in laying hens has always been subject to some controversy. The objective of this study was to evaluate the relative bioavailability of 25-OHD compared to VD₃ in terms of laying performance and egg quality for laying hens from 41 to 48 wk of age. A total of 936 thirty-six-wk-old Roman pink-shell laying hens were fed a basic diet without any additional VD for 5 wk (from wk 36 to 40). Subsequently, A total of 768 hens were selected and randomly assigned to 16 dietary treatments for 8 wk (from wk 41 to 58), including a 0 IU/kg VD control group and groups supplemented with 75, 150, 225, 300, 1600 IU/kg of VD₃, 25-OHD-1 (provided by DSM Ltd.), or 25-OHD-2 (provided by Shandong Haineng Bioengineering Co., Ltd.). The results indicated that increasing VD levels significantly improved the hen day laying rate (HDLR), hen-housed laying rate (HHLR), qualified egg rate, egg weight (EW) and ADFI during wk 45–48 (P < 0.05), and significantly reduced FCR during wk 45–48 (P < 0.05). Compared with VD₃ group, the HDLR and HHLR during wk 45–48 in 25-OHD-1 and 25-OHD-2 group were increased significantly (P < 0.05), and the FCR during wk 45–48 was decreased significantly (P < 0.05). Otherwise, compared with VD 75 IU/kg, the increase of VD level significantly increased the eggshell strength, eggshell thickness and relative weight of eggshell at 44 and 48 wk of age (P < 0.05). The yolk relative weight at 48 wk of age in the VD 75 IU/kg group was significantly higher than that in other groups (P < 0.05). The eggshell strength and relative weight of eggshell at 44 wk of age in the 25-OHD-1 and 25-OHD-2 group were higher (P < 0.05) than those in the VD₃ group. Compared with control group, dietary supplementation with VD improved tibia strength and reduced tibia P content (P < 0.05). The tibia strength in the 25-OHD-2 group was the best among three VD source groups (P < 0.05). Taking VD₃ as 100%, 25-OHD-1 and 25-OHD-2 had relative biological values of 137.6–182.6% and 135.9–195.9% for laying performance, and 108–254.4% and 93–323.5% for eggshell quality, respectively. Overall, the 25-OHD-1 and 25-OHD-2 was approximately 1.6–1.9 times as effective as VD₃ for laying performance and egg quality. The bioavailability of 25-OHD-1 and 25-OHD-2 was no different.