Abstract
This experiment was conducted to investigate the effect of dietary 1α-hydroxycholecalciferol (1α-OH-D(3)) in calcium (Ca)- and phosphorous (P)-deficient diets on growth performance, carcass characteristics, tibia related parameters, and immune responses of broiler chickens. A total of 280 one-day-old broiler chickens (Ross 308) were assigned to 20 floor pens and 4 dietary treatments with 5 replicates. Dietary treatments consisted of starter diets (starter diet of treatment A: 1% Ca, 0.73% total phosphorus [tP]; starter diet of treatment B: 0.85% Ca, 0.64% tP + 5 μg/kg of 1α-OH-D(3); starter diet of treatment C: 0.85% Ca, 0.59% tP + 5 μg/kg of 1α-OH-D(3); starter diet of treatment D: 0.85% Ca, 0.54% tP + 5 μg/kg of 1α-OH-D(3)), grower diets (grower diet of treatment A: 0.86% Ca, 0.68% tP; grower diet of treatment B: 0.73% Ca, 0.59% tP + 5 μg/kg of 1α-OH-D(3); grower diet of treatment C: 0.73% Ca, 0.55% tP + 5 μg/kg of 1α-OH-D(3); grower diet of treatment D: 0.73% Ca, 0.50% tP + 5 μg/kg of 1α-OH-D(3)) and finisher diets (finisher diet of treatment A: 0.81% Ca, 0.64% tP; finisher diet of treatment B: 0.68% Ca, 0.56% tP + 5 μg/kg of 1α-OH-D(3); finisher diet of treatment C: 0.68% Ca, 0.52% tP + 5 μg/kg of 1α-OH-D(3); finisher diet of treatment D: 0.68% Ca, 0.48% tP + 5 μg/kg of 1α-OH-D(3)). Results showed that body weight gain (BWG) and feed intake (FI) of broilers in treatment B were similar to those of broilers in treatment A at the end of the trial (P < 0.05). Broilers in treatments C and D had lower BWG and FI than those in treatment A during the whole trial (P < 0.05). Feed conversion ratio, carcass traits and relative weight of lymphoid organs were not affected by dietary treatments (P > 0.05). Dietary treatments had no significant effect on antibody titers against Newcastle and Influenza disease viruses as well as sheep red blood cells. Dietary treatments had no significant effects on tibia ash and tibial dyschondroplasia score. Broilers fed Ca-P deficient diets had lower tibia Ca and P than those in treatment A (P < 0.05). In conclusion, results indicated that broilers fed Ca-P deficient diets supplemented with 5 μg/kg 1α-OH-D(3) failed to achieve the same tibia Ca and P values as broilers fed nonphytate phosphorus adequate diets.