Comparison of Bioavailability of 1-Hydroxycholecalciferol and Cholecalciferol in Broiler Chicken Diets

The present study aims to compare the relative bioavailability (RBV) of 1-hydroxycholecalciferol (1-OH-D) to cholecalciferol (D) in 1- to 21-d-old broiler chicks fed with calcium (Ca)- and phosphorus (P)-deficient diets. A total of 400 male of 1-d-old Ross 308 broilers were randomly assigned to 8 treatments with 5 replicates each. Five levels of D (0, 2.5, 5, 10, and 20 g/kg) and three levels of 1-OH-D (1.25, 2.5, and 5 g/kg) were added to a basal diet. The basal diet contained 0.50% Ca and 0.25% non-phytate phosphorus (NPP), without D. The RBV of 1-OHD to D was determined by the slope ratio method. Using bodyweight gain, feed intake, feed efficiency, and plasma Ca as criteria, the RBV of 1-OH-D to D were 4.78, 4.75, 4.50, and 4.21, respectively. Using tibia breaking-strength, weight, length, width, ash weight and content, and Ca and P content as criteria, the RBV of 1-OH-D to D were 5.58, 5.16, 4.42, 4.70, 5.03, 4.46, 4.70, and 4.79. Using femur weight, length, width, ash weight and content, and Ca and P content as criteria, the RBV of 1-OH-D to D were 5.09, 4.43, 3.19, 5.83, 5.21, 5.27, and 5.31. Using metatarsus weight, length, width, ash weight and content, and Ca and P content as criteria, the RBV of 1-OHD to D were 5.00, 4.05, 5.94, 4.73, 5.33, 5.64, and 4.28. These data indicate that the RBV of 1-OH-D to D is 4.84 in promoting growth performance and bone mineralization in broilers from 1 to 21 d of age.