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A nine-week feeding experiment was conducted in flow-through system with gibel carp (43.8 ± 0.2 g) 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 15.8 g 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 7.4 g 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 7.4 g kg−1 P. Plasma triglycerides was lower in fish fed diets containing 6.1-10.1 g 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 6.72 g kg−1, respectively. [ABSTRACT FROM AUTHOR]

A 11-week growth trial was conducted in a flow-through system with juvenile gibel carp Carassius auratus gibelio to evaluate the effects of gradual replacement of fish meal (FM) by meat and bone meal (MBM) on growth performance, phosphorus (P) and nitrogen (N) loading. Six isonitrogenous (crude protein: 410 g kg−1) and isoenergetic (gross energy: 18 kJ g−1) diets were formulated. FM was used as the control protein. In the other five diets, 20, 40, 60, 80 and 100% FM protein was substituted with MBM20, MBM40, MBM60, MBM80, MBM100, respectively. Total P content in the diets ranged from 16.0 to 28.3 g kg−1 and the available P was 5.0–6.6 g kg−1. The results showed that the best growth was achieved with fish fed on the control diet and MBM20. Final body weight, weight gain, feed efficiency, protein retention efficiency and energy retention efficiency decreased with increased dietary MBM. No significant differences were found in the feeding rate and hepatosomatic index between the groups. Apparent digestibility coefficient (ADC) of dry matter, protein and P decreased with increase in dietary MBM, while there were no significant differences in the ADC of energy. P and N retention decreased linearly while P and N loading increased linearly with the increased dietary MBM levels. No significant differences were observed in the activity of alkaline phosphatase, aspartate aminotransferase and alanine aminotransferase, as well as pyruvate kinase in liver or in serum. Total superoxide dismutase activity in MBM20 was significantly higher than that of MBM100. [ABSTRACT FROM AUTHOR]