Performance and bone development in broiler chickens given 25-hydroxycholecalciferol

1. A series of 5 trials was conducted with Cobb chickens in order to determine the effect of 25-hydroxycholecalciferol (25OHD(3)) on their performance and bone development under adequate Calcium (Ca) and Phosphorus (P) supplementation, and under moderate dietary restriction of Ca and P. Formulated beadlets of 25OHD(3), trade name HY-D (IsoGen, Naperville, IL, USA) were used as the 25OHD(3) source. 2. Five to 10 mug of cholecalciferol (vitamin D-3) or 25OHD(3)/kg diet were sufficient to ensure normal body weight (BW) and bone ash in chickens under continuous lighting. The two materials had similar effects on BW and bone ash. 3. In one out of the three experiments, 25OHD(3) increased BW and BW gain, while in the others it had a similar effect to that of vitamin D-3, or even a slight negative effect in a trial conducted on the floor, in which the diets were supplemented with the D sources at 75 mug/kg. The effects of both D sources on bone ash and on the severity or frequency of tibial dischondroplasia were similar. 4. 25OHD(3) restrained the effect of moderate dietary P restriction, but not of Ca restriction, on BW gain and bone ash in 22-d-old chickens. This effect could not be explained by an higher P bioavailability in the 25OHD(3)-fed chickens.