Dietary vitamin D3 requirement of Chinese yellow-feathered broilers

Abstract

Three experiments have been conducted to investigate the effects of graded dietary levels of vitamin D3 (VD3) on growth performance, metabolic regulation of calcium (Ca), phosphorus (P), and bone development of Chinese yellow-feathered broilers during 3 growth phases: 1 to 21 d, 22 to 42 d, and 43 to 63 d. Dietary Ca and P in the corn-soybean-based diet were adequate. A total of 2,000 1-day-old, 1,600 22-day-old, and 1,600 43-day- old Lingnan yellow male broilers were randomly assigned to 1 of 8 dietary treatments with 5 replicates per treatment (50 birds per replicate for 1 to 21 d, 40 birds for both 22 to 42 d and 43 to 63 d). Dietary levels of VD3 were 100, 200, 300, 400, 500, 600, and 700 IU/kg for treatments 2 to 8 through the addition of VD3 to the basal mash diet which otherwise lacked detectable VD3. Graded doses of VD3 from 0 to 700 IU/kg in the diet produced linear (P < 0.01) positive responses in ADG, ADFI, tibial weight, and breaking strength, and quadratic (P < 0.01) responses in tibial length, bone density, ash, the levels of Ca and P in the ash , and the ratio of Ca to P. Serum concentrations of Ca, P, 25-hydroxycholecalciferol, osteocalcin, and calcitonin increased, and concentrations of fibroblast growth factor 23, Klotho protein, and parathyroid hormone all decreased with the increasing level of dietary VD3 (P < 0.05). Adding VD3 improved meat color a* value and decreased shear force and drip loss of birds at 63 d (P < 0.05). Considering bone characteristics and composition under the conditions of this study, it was concluded that the VD3 requirements of Chinese yellow-feathered broilers from 1 to 21 d for optimal tibial ash content were estimated from regression analysis to be 464 IU/kg from 1 to 21 d, 539 IU/kg from 22 to 42 d, and 500 IU/kg from 43 to 63 d.