Effects of two commercial feeds with high and low crude protein content on the performance of white shrimp Litopenaeus vannamei raised in an integrated biofloc system with the seaweed Gracilaria birdiae

A trial was conducted for 42 days to evaluate the effects of two commercial feeds with high and low crude protein content on the performance of white shrimp Litopenaeus vannamei cultivated in an integrated biofloc system with the seaweed Gracilaria birdiae. The experiment had a 2 x 2 factorial design (a biofloc monoculture or an integrated system with 32% (low) or 40% (high) crude protein content) with the following treatments: IS32 (an integrated system using low protein commercial feed); IS40 (an integrated system using high protein commercial feed); M32 (a monoculture system using low protein commercial feed); and M40 (a monoculture system using high protein commercial feed), all in triplicate. Shrimp individuals (0.23 +/- 0.04 g) were stocked at a density of 500 shrimp/m(3) and no water exchange was carried out during the experimental period. No significant influence (p > 0.05) was found to be caused by the integrated system or the crude protein levels on water quality. However, a significant influence (p < 0.05) was found for final weight (3.21-4.12 g), weight gain (2.97-3.89 g), yield (1.39-1.96 kg/m(3)) and feed conversion ratio (1.47-1.74). Growth was similar in IS32, M40 and IS40, indicating that crude protein levels can be reduced with no adverse effect on shrimp performance variables in integrated biofloc systems with G. birdiae.