Effects of dietary protein and water exchange on water quality, survival and growth of postlarvae and juvenile Litopenaeus vannamei

Two growth trials were conducted with Litopenaeus vannamei to evaluate effects of dietary protein and water exchange on survival, growth and water quality. In both trials, protein levels were 12, 15, 20, 26 and 35%. In the first trial, 6.21 g juvenile shrimp were stocked for 23 days at either zero or high (2750% daily) water exchange. At high exchange, survival was greater than 93% for all protein levels. Final body weight (FBW) and weight gain (WG) increased with protein level from 12% to 20% (P < 0.05). FBW and WG at 20 and 26% protein were lower than that at 35% protein. At zero exchange, survival decreased with protein above 20%. At zero exchange, water quality decreased (high ammonia, nitrite, nitrate and low pH, alkalinity) with protein greater than 15%. WG with 12% protein was greater at zero exchange than at high exchange. In the second trial, 0.22 g postlarvae were stocked for 26 days at either zero or high (5440% daily) water exchange. At high exchange, survival was 90% or greater for all protein levels. FBW and WG increased with protein level from 12% to 20% (P < 0.05). At zero exchange, FBW and WG were maximum with 20% protein. Survival was lowest at 35% protein. For 35% protein, survival was lower at zero than at high exchange. For all protein levels except 35%, WG was higher at zero than at high exchange. The results suggest that lower protein diets can replace high protein (35%) commercial diets and obtain high growth rate for both juvenile and postlarvae L. vannamei at zero exchange. Further, a 20% protein diet, which contained 25.3% marine animal meals, was adequate for shrimp growth, survival and water quality at zero exchange.