Abstract

1. The effects of graded amounts of dietary ascorbic acid with or without 10 μg/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 μg/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. Gakv.food was increased when 250 or 500 mg ascorbic acid/kg diet were added along with 10 μg/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‐hydroxycholecalcif‐erol 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.