Safety of 25-hydroxyvitamin D3 as a source of vitamin D3 in turkey rations

A target animal safety study investigated the effects of providing 25-hydroxyvitamin D3 (25-OH-D3) as a replacement for vitamin D3 in pelleted turkey feeds. Five groups of turkeys were fed diets containing vitamin D3 at 68.9 micrograms/kg feed (control) or 25-OH-D3 at concentrations of 49.5 (0.5x), 99 (1x), 495 (5x) or 990 (10x) micrograms 25-OH-D3/kg feed. The effects of 25-OH-D3 or vitamin D3 on performance, health, hematology, gross pathology and tissue concentrations of 25-OH-D3 in female and male turkeys were compared at 112 days of feeding. There was no significant difference from control in pen body weight in any of the groups. When feed conversion was calculated without taking into account body weights of birds that died during the study, there was no significant difference from control in any of the groups. When feed conversion was corrected for mortality, the only significant effect was that females at the 5x level (495 micrograms 25-OH-D3/kg feed) had improved feed conversion. Significantly increased mortality occurred during the study in the 10x (990 micrograms 25-OH-D3/kg feed) male group only. No histomorphologic tissue alterations attributable to dietary administration of 25-OH-D3 were observed in tissues examined at any dietary level of 25-OH-D3. 25-OH-D3 did not adversely affect animal health at the proposed use level of 99 micrograms/kg feed when replacing vitamin D3 in turkey rations. The proposed use level also provides at least a 5-fold margin of safety.