Dietary available phosphorus requirement for on-growing gibel carp (Carassius auratus gibeliovar. CAS III)

A nine-week feeding experiment was conducted in flow-through system with gibel carp (43.8 +/- 0.2g) to study the effects of dietary available phosphorus (P) on growth, phosphorous digestibility and intestinal enzyme activities. Seven semipurified diets were formulated to contain 0.8 (the basal), 2.4, 3.6, 6.1, 7.4, 10.1 and 15.8g available phosphorus kg(-1) diet. The results showed that specific growth rate and feed efficiency increased with increasing dietary available P from 0.8 to 7.4g P kg(-1). Fish body ash increased with increasing dietary available P, while moisture, protein content or energy content had no difference. Total phosphorus waste discharging (TPW) increased with increased dietary phosphorous. Plasma glucose was higher in the fish fed with 7.4g kg(-1) P. Plasma triglycerides was lower in fish fed diets containing 6.1-10.1g kg(-1) P. No significant effects were observed in plasma P and Ca (p>.05). The activities of intestinal amylase, lipase and trypsin showed no difference, while AKP and Na+, K+-ATPase activities decreased with increasing dietary available P. In conclusion, based on the regression between specific growth rate (SGR), P retention efficiency, feed efficiency (FE) and dietary available P, the available P requirements for on-growing gibel carp were 10.69, 8.22 and 6.72g kg(-1), respectively.