CAJ | 학술논문

A 3 × 4 factorial experiment was con-ducted to determine the effect of dietary nutrient den-sity on growth performance, physiological parame-ters, and small intestinal epithelial phosphate trans-porter expression in broiler chicks fed different dietary nutrient density(DND)and non-phytate phosphorus (NPP)levels. Dietary energy densities used had ME values of 2,850, 2,950, and 3,050 kcal/kg of diet and the NPP levels were 0.35%, 0.40%, 0.45%,and 0.50% within each ME value. Crude protein and essential amino acids levels were maintained propor-tionally to dietary ME levels. Each of the twelve diets was fed to five pens of seven male broiler chicks from 1 to 21 days of age. Broiler growth performance, ser-um physiological parameters, 1-hydroxylase activity in the kidney, type-lib sodium phosphate co-trans-porter(NaPi-IIb), and vitamin D receptor(VDR)expression levels in the duodenal mucosa were deter-mined. Our results showed that an increase in dietary nutrient density increased body weight and improved feed conversion. Additionally, serum parathyroid hormone concentration, 1-α-hydroxylase activity in the kidney, NaPi-IIb mRNA expression and VDR protein expression in the duodenal mucosa increased as DND increased. Feed intake and body weight in-creased as NPP levels increased. Serum parathyroid hormone, VDR and NaPi-IIb gene expression also in-creased as the level of NPP in the diet increased at the medium range level. The results of this study suggest that high DND can increase small intestinal type IIb sodium dependent phosphate co-transporter mRNA expression by up-regulating parathyroid hormone and activation of 1-α-hydroxylase activity which might be in consistent with high growth rate of broilers. Small intestinal NaPi-IIb mRNA expression increases linear-ly only within the range of dietary NPP dosage levels close to the requirement recommended in the broilers feeding standards.