Vitamin D₃ (VD₃) is essential for calcium and phosphorus absorption and bone development. However, endogenous synthesis of VD₃ in poultry is insufficient to meet growth requirements, necessitating dietary supplementation. NRC (1994) recommended VD₃ requirements for both starter and growing White Pekin ducks were 400 IU/kg. With the increasing growth rate of meat ducks, NRC recommendations may be inadequate for the growth of modern meat ducks. Our previous results have shown VD₃ requirements for starter male White Pekin ducks were 233 to 633 IU/kg, but the requirements for growing Pekin ducks remain unclear. 25-Hydroxycholecalciferol (25-OH-D₃) is the main circulating form of VD₃ in the blood, is more readily utilized than VD₃. However, its bioavailability in growing Pekin ducks remains unexamined. This study aimed to determine VD₃ and 25-OH-D₃ requirements in growing male White Pekin ducks and relative bioavailability of these 2 compounds. The results showed that VD₃ and 25-OH-D₃ requirements for growing Pekin ducks were 698 IU/kg and 352 IU/kg, respectively. The relative bioavailability of 25-OH-D₃ compared to VD₃ was 188%, based on slope-ratio comparisons from multiple linear regressions of plasma 25-OH-D₃ concentrations.

Read the full article in the Journal of Animal Science.