Dietary Calcium Levels Reduce the Efficacy of One Alpha-Hydroxycholecalciferol in Phosphorus-Deficient Diets of Broilers

Abstract

One alpha-hydroxycholecalciferol (1α-OH D₃), an analog of cholecalciferol (vitamin D₃), improves growth performance and phosphorus retention in broilers. In the present study, we investigate the effects of dietary calcium (Ca) levels on the efficacy of 1α-OH D3 in the phosphorus (P)-deficient corn-soybean meal diets of 1- to 21-d-old broilers. Four hundred female Ross 308 broilers, 1-d-old, were randomly allotted to 10 treatments with 4 cages of 10 birds each. A 5×2 factorial experiment was designed to test 0.40, 0.60, 0.80, 1.00, and 1.20% Ca combined with 0 and 5μg/kg of 1α-OH D₃ in a basal diet (0.25% non-phytate phosphorus (NPP), 0.48% total phosphorus (tP)) without vitamin D₃. The lowest levels of body weight gain (BWG), feed intake (FI), feed efficiency (FE), tibia quality (except of ash and P), as well as the highest value of mortality, were observed at 0.40% Ca. Additional Ca corrected the Ca deficiency and eventually 1.2% Ca caused a P deficiency. The addition of 1α-OH D₃ improved BWG, FI, FE, serum inorganic phosphate concentration, tP retention, tibia weight, length, breaking-strength, and content of ash, Ca, and P, and decreased mortality. However, 1α-OH D₃ efficacy responded negatively to dietary Ca level. These results indicate that 1α-OH D₃ exerts the highest activities at lower concentration of dietary Ca.