Effects of ascorbic acid and 1,25-dihydroxycholecalciferol on alkaline phosphatase and tibial dyschondroplasia in broiler chickens.

1. The effects of graded amounts of dietary ascorbic acid with or without 10 micrograms/kg dietary 1,25-dihydroxycholecalciferol on performance, blood and bone variables were measured in broiler chicks. 2. 1,25-Dihydroxycholecalciferol prevented the tibial dyschondroplasia and rickets caused by feeding a low calcium diet. Gain:food was decreased, but body weight was not affected by feeding 10 micrograms/kg 1,25-dihydroxycholecalciferol. Phytate phosphorus retention was increased by dietary 1,25-dihydroxycholecalciferol. 3. Dietary ascorbic acid did not influence the incidence of tibial dyschondroplasia, but did reduce the incidence of rickets at a dietary concentration of 250 mg/kg. Gain:food was increased when 250 or 500 mg ascorbic acid/kg diet were added along with 10 micrograms/kg 1,25-dihydroxycholecalciferol in one of two experiments. 4. Alkaline phosphatase activity and plasma 1,25-dihydroxycholecalciferol were not affected by the dietary treatments. Plasma 25-hydroxycholecalciferol concentration was decreased by dietary 1,25-dihydroxycholecalciferol. 5. Ascorbic acid had no synergistic effects with 1,25-dihydroxycholecalciferol on the blood and bone variables investigated in broiler chickens at the dietary concentrations of 1,25-dihydroxycholecalciferol used in this work.