Common problems in poultry production are bone and joint diseases due to insufficient bone mineralization. To prevent these problems, DSM Nutritional Products offers Hy-D®. This product contains 25-hydroxy-cholecalciferol, which is naturally synthesized in the liver from cholecalciferol (vitamin D3). Oral supplementation with this product makes this step unnecessary and might therefore lead to better bone mineralization, enhanced wellbeing and better performance. Aim of the current study was to investigate the effect of an oral supplementation with Hy-D® on bone metabolism and performance in broilers and broiler breeders. A total of 101,000 birds were used (69,500 broilers and 31,500 breeders). Animals were divided into two groups. In one group, half of the vitamin D3 in the feed was replaced by Hy-D®, the other group received only vitamin D3. We measured the concentration of calcium, phosphorous and magnesium and the activity of alkaline phosphatase in plasma, the concentration of calcium, phosphorous and magnesium in the bone, bone stability, bone diameter of the tibiotarsus, weight gain and feed efficiency. In broilers, the supplementation with Hy-D® led to a significant increase of the bone calcium concentration of 6 %, a significant increase in bone stability by 19.7 %, and a significant increase in bone diameter by 12 %. Feed efficiency was 6 % higher in the experimental group, while losses were 1.2 % higher in the control group. Thus, the experimental group resulted in a 25 % higher gross yield, calculated from the meat yield minus the costs for animals and feed. However, the gross yield is also influenced by the time of slaughter, which could not be predetermined in the present experiment. In the broiler breeders, no influences of Hy-D® supplementation were seen.