Dietary phosphorus requirement for juvenile bighead carp (Aristichthys nobilis)

A 60-day feeding trial was conducted to estimate the optimum phosphorus requirement of juvenile bighead carp (Aristichthys nobilis). Fish (initial body weight: 2.42 +/- 0.08 g) were hand-fed with six isoproteic (437 g kg(-1)) and isolipidic (68 g kg(-1)) diets containing graded phosphorus levels (0.90, 4.40, 8.30, 11.90, 15.50, and 19.30 g kg(-1)) thrice daily to apparent satiation. Each diet was randomly assigned to triplicate tanks, and each tank was stocked with 30 fish. The highest weight gain rate (WGR, 288.94%) and specific growth rate (2.28% day(-1)) and the best feed conversion rate (FCR, 1.91) were recorded in fish fed 8.30 g kg(-1) phosphorus. The body composition analysis showed that the phosphorus contents in the whole body, muscle, vertebra, and plasma of fish fed the phosphorus-supplemented diets were higher than those of fish fed the control diet, whereas the phosphorus retention rate and crude lipid contents in the whole body and muscle presented the reverse results. The highest activity of lipase (41.97 U g(-1) prot) in the intestine was found in fish fed the diet with 11.90 g kg(-1) phosphorus. Further, the contents of total protein, albumin, and globulin in plasma were increased as dietary phosphorus levels ranged from 0.90 to 11.90 g kg(-1) and then decreased with further increased phosphorus levels. The highest contents of triglyceride (1.85 mmol L-1) and total cholesterol (2.16 mmol L-1) in plasma occurred at dietary phosphorus level of 0.90 g kg(-1). Broken-line model analysis based on WGR, FCR, and the phosphorus contents of the whole body and vertebra indicated that the optimal phosphorus requirements for juvenile bighead carp were 7.16, 9.02, 10.88, and 11.04 g kg(-1), respectively.

Automated summary

A 60-day feeding trial was conducted to determine the optimum phosphorus requirement for juvenile bighead carp. It was found that supplementing the diets with phosphorus improved weight gain, specific growth rate, and feed conversion rate. Moreover, the phosphorus content and lipase activity in the fish's body also increased with dietary phosphorus levels.