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 with out 10 mu g/kg dietary 1,25-dihydroxycholecalciferol on performance, b lood and bone variables were measured in broiler chicks. 2. 1,25-Dihyd roxycholecalciferol prevented the tibial dyschondroplasia and rickets caused by feeding a low calcium diet. Gain:food was decreased, but bod y weight was not affected by feeding 10 mu g/kg 1,25-dihydroxycholecal ciferol. Phytate phosphorus retention was increased by dietary 1,25-di hydroxycholecalciferol. 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 increa sed when 250 or 500 mg ascorbic acid/kg diet were added along with 10 mu g/kg 1,25-dihydroxycholecalciferol in one of two experiments. 4. Al kaline phosphatase activity and plasma 1,25-dihydroxycholecalciferol w ere not affected by the dietary treatments. Plasma 25-hydroxycholecalc iferol concentration was decreased by dietary 1,25-dihydroxycholecalci ferol. 5. Ascorbic acid had no synergistic effects with 1,25-dihydroxy cholecalciferol on the blood and bone variables investigated in broile r chickens at the dietary concentrations of 1,25-dihydroxycholecalcife rol used in this work.