Effect of dietary phosphorus sources and varying levels of supplemental phosphorus on survival, growth and body composition of postlarval shrimp (Litopenaeus vannamei)

Two experiments were conducted for 30 days each to investigate the effective phosphorus source and supplemental phosphorus levels for postlarval Litopenaeus vannamei. The first experiment was performed in postlarval shrimp (mean initial wet weight 2 mg) fed four isoenergic and isonitrogenous diets containing three supplemented inorganic phosphorus sources [D1: no supplemental phosphorus, D2: NaH2PO4·2H2O, D3: KH2PO4·2H2O, D4: Ca(H2PO4)2·2H2O]. The quantities of the three supplemental NaH2PO4·2H2O, KH2PO4·2H2O and Ca(H2PO4)2·2H2O were 11.6, 12.8 and 10 g kg−1 of the diet, respectively in order to make the three diets have the same total phosphorus. Growth performance (final mean body weight, FBW; weight gain, WG; specific growth ratio, SGR) of shrimp in D3 treatment was the highest and had significant difference with the D1 treatment. The survival of shrimp in D3 treatment was the highest and had significant difference with the other treatments. The mineral concentration and body composition of shrimp were not significantly different among treatments. We could conclude that KH2PO4·2H2O was the optimal phosphorus source for postlarval L. vannamei from the growth performance and survival. The second experiment was performed in postlarval shrimp (mean initial wet weight 0.88 mg) fed four isoenergic and isonitrogenous diets containing four supplemental KH2PO4·2H2O levels (d1, d2, d3 and d4 with 0, 5, 10 and 20 g kg−1, respectively). Shrimp in d2 treatment showed the highest growth performance and survival and also showed significant difference with other diet treatments. The whole body content of zinc (Zn) increased with the increase of dietary KH2PO4·2H2O and significant differences were observed when dietary KH2PO4·2H2O reached 5 g kg−1, excess KH2PO4·2H2O supplementation (10 and 20 g kg−1) had a negative effect on Zn content, the Zn content significantly decreased when KH2PO4·2H2O was 20 g kg−1. We can conclude that the amount of total phosphorus in the diet should be maintained between 20.9 and 22.0 g kg−1, the amount of supplemental KH2PO4·2H2O in the diet is less than 10 g kg−1.