Phosphorus requirement of common carp (Cyprinus carpio L) based on growth and mineralization

The effect of diets supplemented with varied levels of inorganic phosphorus (P) (NaH2PO4) on the growth, body composition, nutrient digestibility and mineralization in common carp (Cyprinus carpio L) was evaluated to determine the optimum P requirements. The six diets used were DPO, as the basal diet with a total P content of 1.30 g kg-1, and DP1, DP2, DP3, DP4 and DP5, which contained 4.10, 6.70, 11.6, 14.9 and 23.4 g P kg-1 respectively. Weight gain, SGR, apparent digestibility coefficient of organic matter and P, whole body ash, P, Ca and Mg increased significantly with increasing dietary P levels while dry matter (DM), fat and Zn content decreased. Feed conversion ratio was the poorest (P < 0.05) in fish fed DPO, suggesting P deficiency. The apparent digestibility coefficient of P was 18% in the DPO-fed group, which increased from 69% in DP1 to 92% in DP5 after P supplementation, revealing lower digestibility of the native P than that in NaH2PO4. Broken-line analyses based on weight gain, P content of fish bones and whole body against total dietary and digestible P (data in brackets) contents showed the optimum P requirement for the growth of common carp to be 6.87 (5.55) g kg-1 DM, and the requirement for optimum mineralization in bones and whole body to be 9.10 (7.62) and 14.7 (13.2) g kg-1.