... metabolite of vitamin D3, has more physiological activity. 25 hydroxy vitamin D3, also known as calcifediol, is ... , vitamin D3 can not be directly converted to 25 hydroxy vitamin D3. Even if the amount of ... vitamin D3 intake can not be absorbed, 25 hydroxy vitamin D3 can be an active substance ... absorption for human or animal directly. 2. When 25 hydroxy vitamin D3 used on animals, birds, it can ...