Effects of seawater potassium concentration on the dietary potassium requirement of Litopenaeus vannamei

Abstract

Effects of seawater potassium concentration on the dietary potassium requirement of Litopenaeus vannamei were studied under the condition of artificial seawater at salinity 30‰. Three potassium concentrations in the water were set: 332, 156 and 104 mg l − 1 . And the potassium contents of the casein-gelatin-based experimental diets were 1.09%, 1.53%, 2.49% and 3.46%, respectively. The feeding trial lasted for 56 days. Growth, feeding, nutrient retention and feed conversion efficiency of the shrimp were significantly affected by the potassium concentration in the seawater ( P < 0.05), but the dietary potassium levels showed little effect .The final body weight, specific growth rate, protein efficiency ratio and feed conversion efficiency of shrimp exposed to 104 mg l − 1 water potassium level were, respectively, more than 37%, 26%, 25% and 27.5% lower than of those exposed to higher water potassium levels ( P < 0.05). No significant interaction effects were found between seawater potassium concentration and dietary potassium level. Neither seawater potassium concentrations nor dietary potassium levels influenced the body potassium content. It indicated that L. vannamei may have poor ability of assimilating potassium from dietary sources efficiently at salinity 30‰, and dietary supplementation of potassium had limited effect on improving growth of the shrimp while environmental potassium was sufficient.