Evaluation of the productive and physiological responses of Litopenaeus vannamei infected with WSSV and fed diets enriched with Dunaliella sp.

An experimental investigation was performed to evaluate the productive and physiological responses of Litopenaeus vannamei that were infected with WSSV and fed diets enriched with Dunaliella sp., which had a high ß-carotene content induced by nitrogen reduction in the culture medium. A basal diet containing 35% crude protein and experimental diets T1 and T2, which included 1% and 2% microalgae meal, respectively, were evaluated. Positive (infected juveniles) and negative (non-infected) controls were also evaluated. Survival was significantly higher (80%) in the two treatment groups compared to the positive control group (56%). In the negative control group, survival was 100%. Some variation was recorded for hemolymph metabolites among treatments and at distinct times post-infection; although the tendencies were not clear, some metabolites (glucose and triglycerides) appeared to decrease on the last days of the trial, probably due to their use as energy for the shrimp to thrive despite the infection. The results of the study suggest a positive effect of the dietary inclusion of Dunaliella meal on shrimp survival and an unclear effect on hemolymph metabolites.

Production response and digestive enzymatic activity of the Pacific white shrimp Litopenaeus vannamei (Boone, 1931) intensively pregrown in microbial heterotrophic and autotrophic-based systems.

Shrimp postlarvae were reared into different microcosm systems without water exchange; a traditional system based on simple fertilization to improve microalgae concentration (control), an autotrophic system (AS) based on the promotion of biofloc and biofilm by the addition of fertilizer and artificial substrates and a heterotrophic system (HS) based on the promotion of heterotrophic bacteria by the addition of nitrogenous and carbonaceous sources and artificial substrates. Better growth performance and survival were registered in shrimp from the AS and HS compared to the control. Feed conversion ratios were below 0.7 for all treatments, but AS and HS were significantly lower than the control. Regarding digestive performance, no significant differences were observed for trypsin, amylase and lipase activities among AS and control shrimp; however, shrimp from HS showed a higher trypsin and amylase activities, suggesting a higher digestive activity caused by the presence of microbial bioflocs. The presence of biofilm and bioflocs composed by either autotrophic or heterotrophic organisms in combination with formulated feed improved the growth performance and survival of shrimp. Apparently, such combination fits the nutritional requirements of shrimp.