Dietary available phosphorus requirement for juvenile gibel carp (Carassius auratus gibelio var. CASIII)

A 57‐day growth experiment was conducted with juvenile gibel carp (13.48 ± 0.10 g) in a flow‐through system to study the effect of dietary phosphorus on growth performance, body composition, nutrition utilization, phosphorus loading and enzymes activities. Seven semipurifed diets were formulated to contain 0.07 (the basal), 2.27, 5.32, 8.10, 12.06, 15.24 and 19.48 g available phosphorus/kg diet. The results showed that specific growth rate, body length and feed efficiency significantly increased in the fish fed diets containing 0.07 to 15.24 g available P/kg diet (p < .05). Ash and P content increased in fish fed diets containing 0.07–12.06 P g/kg (p < .05) and then levelled off, while moisture, crude protein and lipid had no significant difference (p > .05). The protein retention efficiency increased in the fish fed with diets 0.07–5.32 g/kg P (p < .05) and then reached a plateau. The P content in faeces was higher in fish fed diets containing 15.24 and 19.48 g available P/kg. Total P concentration in tank water increased in fish fed 0.07–12.06 g available P per kg diet (p < .05). The plasma P was higher in the fish fed with 15.24 g available P/kg diet (p < .05), triglycerides was lower in the fish fed diet containing 15.24 and 19.48 g available P/kg (p < .05), no significant differences were observed in plasma Ca, plasma glucose and calcitonin (p > .05). Based on SGR, whole body P content and FE, dietary available P requirement for juvenile gibel carp were 13.37, 13.97 g/kg and 15.06 respectively.