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 cha racterize further the relation between boron and cholecalciferol. Two 2 X 3 factorially designed experiments were conducted with boron (0 an d 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), noncholecalc iferol-added basal diet. Each diet was fed to 16 broiler chicks divide d in two groups, housed in plastic cages, from 1 d to either 27 d (Exp t 1) or 26 d (Expt 2) of age. In Expt 1, chicks fed the basal diet, co mpared to those fed supplemental cholecalciferol, exhibited rickets an d increased bone concentrations of sodium, potassium, zinc, copper, an d manganese, and reduced bone dry weights and concentrations of iron. Supplemental boron improved growth, feed efficiency, and gait abnormal ities and increased concentrations of serum 25-hydroxycholecalciferol, ionized calcium and triglycerides, and bone iron, and reduced concent rations of bone sodium, potassium, zinc, and copper in chicks fed 3.13 , but not 0 and 15.63, mu g cholecalciferol/kg diet. Supplemental boro n increased bone boron concentrations regardless of cholecalciferol st atus. In Expt 2, the effects of boron on these variables were similar but less pronounced. These findings suggest that boron enhances the ef ficacy of cholecalciferol, but boron does not substitute for the vitam in. Further study is needed to determine whether boron enhances cholec alciferol absorption or hydroxylation. (C) 1997 Wiley-Liss, Inc.