An experiment was conducted to evaluate the effects of 1α-OH-D3 either with or without
Cholecalciferol, microbial phytase as well as different levels of dietary calcium, and phosphorus on
broiler chickens, performance. A number of 576 male broiler chickens (Ross 308) were made use of in
a completely randomized design of a factorial arrangement (3×2×2×3), comprised of 36 treatments, 4
replicates of 4 chicks in each battery cage. Factors included three levels of 1α-OH-D3 (0, 5 and 10
μg/kg), two levels of Cholecalciferol (0 and 5000 ICU/kg), two levels of microbial phytase (0 and 500
FTU/kg), as well as three levels of Ca and phosphorus (100, 75 and 50% of Ross broiler nutrition
recommendation values). Dietary treatments were implemented within an age interval of from 1 to 42
days. Supplementation of diets of 5 and 10 μg/kg of 1α-OH-D3 reduced body weight and feed intake at
7, 35 and 42d (P<0.01; P<0.05). Supplementation of 500 FTU/kg of Phytase enzyme in the diet
increased body weight at 7 and 14 days (P<0.05). Interaction between 1α-OH-D3 and phytase on feed
conversion ratio was significant (P<0.01), in a way that addition of 500 FTU/kg of Phytase to diet
containing 5 μg/kg of 1α-OH-D3 improved feed conversion ratio at 28d (P≤0.01). 1α-OH-D3
supplementation increased tibia breaking force, linearly (P<0.01). Results indicated that addition of
1α-OH-D3 to broiler chickens, diets alleviates the risk of tibial dyschondroplasia incidence. Yet, the
appropriate recommended dosage needs to be further investigated.