Abstract
A study was conducted to evaluate the effect of dietary 25-hydroxyvitamin D(3) (25OHD) on pullet and egg-laying hen growth performance, egg production, and egg quality. Three hundred and ninety 1-day-old Hy-Line W36 pullets were randomly allocated to 3 treatments with 10 replicated cages and 13 birds per cage. Dietary treatments were vitamin D(3) at 2,760 IU/kg (D); vitamin D(3) at 5,520 IU/kg (DD), and vitamin D(3) at 2,760 IU/kg plus 25OHD at 2,760 IU (69 μg)/kg (25D). Body weight and feed intake were recorded at the end of each stage: starter 1 (0-3 wk), starter 2 (4-6 wk), grower (7-12 wk), developer (13-15 wk), prelay (15-17 wk), peaking (18-38 wk), layer 2 (39-48 wk), layer 3 (49-60 wk), layer 4 (61-75 wk), and layer 5 (76-95 wk). Egg production was recorded daily. Egg quality was evaluated every 8 wk starting from 25 wk. There was no difference in growth performance during the rearing period (0-17 wk). In the laying period (18-95 wk), DD showed lower feed intake at layer 2, but higher intake at layer 3 along with lower hen day production (HDP) from 22 to 48 wk compared to the other treatments. During the same period, the DD group laid smaller eggs with higher specific gravity and shell thickness compared with the other treatments or D alone at 40 wk, which may be partly due to the lower body weight. In contrast, 25D had better feed conversion ratio (feed intake per dozen of eggs) at layer 2, and higher overall (22-60 wk) HDP compared with DD. For the egg quality analysis, at 25 and 33 wk, both DD and 25D had higher Haugh unit compared with D. However, 25OHD has no effects on eggshell quality during the entire production period and no beneficial effects on egg production during the later laying period (after 60 wk). In summary, long-term and early supplementation of 25OHD has positive effects on egg production and egg quality, and the beneficial effects were mainly observed during the early laying stage.