Effect of constant 2:1 calcium to non-phytate phosphorus ratio over a range of concentrations during starter-grower and finisher phases on performance of broiler chicken

Abstract

This experiment investigated the effect of 2:1 ratio of calcium (Ca) to non-phytate phosphorus (NPP) over a range of their concentrations on performance of broilers in phase 1 (1–24 days), phase 2 (25–38 days) and the whole period. A total of 900 male broilers were allocated into 60 pens. In phase 1, dietary treatments were high (H, 9.6 g/kg Ca and 4.8 g/kg NPP), moderate (M, 7.6 g/kg Ca and 3.8 g/kg NPP), low (L, 5.6 g/kg Ca and 2.8 g/kg NPP) and very low (VL, 3.6 g/kg Ca and 1.8 g/kg) level of Ca and NPP. H and M diets showed higher average daily feed intake (ADFI) and serum Ca than those of L and VL diets. There was a linear decrease in tibia Ca and serum P and a linear increase in relative expression of SLC20A1 and CALB1 and retention of Ca and P when concentration of Ca and NPP was reduced. H diet resulted in the highest tarsometatarsus strength and feed conversion ratio (FCR). M and L diets showed higher average daily gain (ADG) than those of H and VL diets. VL diet demonstrated the lowest tibia ash. On day 25, treatments H, M, L and VL received, respectively, 4, 3, 2 and 1 types of finisher diets (H, M, L and VL) during phase 2, resulting in a total of 10 treatments; HH, HM, HL, HVL, MM, ML, MVL, LL, LVL and VLVL. HH vs. HM vs. HL vs. HVL showed a linear decrease of ADFI, ADG, serum P, tibia ash, tarsometatarsus strength and a linear increase of FCR. HH vs. MM vs. LL vs. VLVL demonstrated a linear increase of relative expression of CALB1 and SLC20A1 and a linear decrease of serum P, and in terms of growth performance, MM showed the best results generally. MM vs. ML vs. MVL showed a linear decrease of ADFI and ADG and a linear increase of FCR. HM vs. ML vs. LVL demonstrated a linear decrease of ADG, serum Ca and P and relative expression of CALB1 and a linear increase of FCR (during phase 2). In conclusion, reducing Ca and NPP level over finisher phase, similarly for all combinations of treatments, resulted in poorer performance either in finisher phase or the whole period. Generally, 7.6 g/kg Ca and 3.8 g/kg NPP over the whole period maximized broiler’s performance without negative effects on bone ash and strength.