Biofloc technology (BFT) is a microbial manipulation technique used recently in intensive shrimp aquaculture.
The driving force of BFT culture systems is microbial biofloc that is responsible for enhancing water
quality, supplementing natural food, and improving growth and health of cultured shrimp. The aim of this
study was to investigate the effects of biofloc on immune response and antioxidant status of Litopenaeus
vannamei juveniles reared in biofloc-based tanks through manipulating high C/N ratio of feed input. Two
biofloc treatments and one control were compared: Biofloc-based tanks under zero-water exchange with
two levels of C/N ratio (15:1, 20:1) by addition of carbohydrate referred to as ‘CN15’ and ‘CN20’ and clear
water tanks operated with high water exchange and without addition of carbohydrate referred to as ‘control’.
The shrimp were cultured for 30 days. The water quality in biofloc-based tanks was maintained with the promotion
and development of biofloc through sucrose addition during the experiment. At the end of the experiment,
the total hemocyte count in the hemolymph and the phagocytic activity of the hemocyte of the shrimp
in the two biofloc treatments were significantly higher than those of the shrimp in the control group
(P b 0.05). Furthermore, the total antioxidant capacity in both the plasma and the hepatopancreas of the
shrimp in the two biofloc treatments was significantly higher than those of the shrimp in the control
group (P b 0.05). Increased superoxide dismutase activity in the plasma, and increased reduced/oxidized glutathione
ratio in both the plasma and the hepatopancreas were found in the shrimp of the two biofloc treatments
(P b 0.05). There were no significant differences in all of the above parameters between the CN15 and
CN20 treatments (P N 0.05). The results indicated that promoting biofloc through carbohydrate addition in
zero-water exchange systems could enhance immune cellular response and antioxidant status of cultured
shrimp under the conditions of the present study.