Dietary boron enhances efficacy of cholecalciferol in broiler chicks

Accumulating evidence suggests that boron influences the metabolism of cholecalciferol in humans and animals. This study was designed to characterize further the relation between boron and cholecalciferol. Two 2 X 3 factorially designed experiments were conducted with boron (0 and 3 mg/kg) and cholecalciferol [0, 3.13 (Expt 1) or 5.0 (Expt 2), and 15.63 mu g/kg] supplemented to a low-boron (<0.18 mg/kg), noncholecalciferol-added basal diet. Each diet was fed to 16 broiler chicks divided in two groups, housed in plastic cages, from 1 d to either 27 d (Expt 1) or 26 d (Expt 2) of age. In Expt 1, chicks fed the basal diet, compared to those fed supplemental cholecalciferol, exhibited rickets and increased bone concentrations of sodium, potassium, zinc, copper, and manganese, and reduced bone dry weights and concentrations of iron. Supplemental boron improved growth, feed efficiency, and gait abnormalities and increased concentrations of serum 25-hydroxycholecalciferol, ionized calcium and triglycerides, and bone iron, and reduced concentrations of bone sodium, potassium, zinc, and copper in chicks fed 3.13, but not 0 and 15.63, mu g cholecalciferol/kg diet. Supplemental boron increased bone boron concentrations regardless of cholecalciferol status. In Expt 2, the effects of boron on these variables were similar but less pronounced. These findings suggest that boron enhances the efficacy of cholecalciferol, but boron does not substitute for the vitamin. Further study is needed to determine whether boron enhances cholecalciferol absorption or hydroxylation. (C) 1997 Wiley-Liss, Inc.