Effects of bioflocs on growth performance, digestive enzyme activity and body composition of juvenile Litopenaeus vannamei in zero-water exchange tanks manipulating C/N ratio in feed.

摘要

A 30-day feeding experiment was conducted to investigate the effects of promoted bioflocs on growth performance, feed utilization, digestive enzyme activity and whole body composition of Litopenaeus vannamei juveniles (average 6.95+or-0.22 g) in zero-water exchange culture tanks. Two bioflocs treatments and one control were evaluated: Bioflocs-based tanks with two levels of C/N ratio (15, 20) by addition of carbohydrate referred to as 'CN15' and 'CN20', and clear water tanks operated with water exchange and without addition of carbohydrate referred to as 'Control'. Each group consisted of quadruplicate tanks (125 L) and each tank contained 28 shrimp (equivalent to shrimp density of 224 individuals and biomass of ~ 1.56 kg per cubic meter of water volume). Original concentrated bioflocs were collected from an indoor bioflocs-based shrimp culture pond, and inoculated into all bioflocs-based tanks with the same amount (0.5 mL L-1 bioflocs volume) just before stocking shrimp. Sucrose was applied as a source of carbohydrate and added separately to the CN15 and CN20 treatment tanks in addition to the applied feed (35% crude protein), so as to raise the C/N ratio of the feeds input (feed and sucrose) to 15 and 20 and subsequently promote the development of bioflocs. The monitoring of water quality parameters showed that they all remained within recommended levels for shrimp culture in the three groups. At the end of the experiment, survival rates of the shrimp were above 90%, with no significant differences among the three groups (P