were found in the liver trypsin and amylase activities of fish between
the two groups (P N 0.05). However, the lipase activity in the liver of
fish cultured in the BFT treatment was significantly higher than that in
the control group (P b 0.05). There were no significant differences in
the trypsin and lipase activities in the fish intestines between the BFT
treatment and the control group (P N 0.05), whereas the intestine
amylase activity of fish cultured in the BFT tanks was significantly
higher than that in the control tanks (P b 0.05).
It is possible that biofloc plays a role in stimulating the activities of
digestive enzymes (Moss et al., 2001; Xu et al., 2012a,b). In addition,
Xu and Pan (2012) found that biofloc displayed relatively high amylase
activities, which may account for the increased intestinal amylase
activity of fish growing in the BFT treatment in this study. Furthermore,
enhanced liver lipasemay facilitate the digestion and utilization of lipid,
which could have increased the crude lipid content of tilapia in the BFT
group. It is evident that the enzyme activities were tissue-specific,
i.e., highest in the liver and lowest in the intestine. The BFT treatment
had a stimulatory effect on the digestive enzyme activities, which may
have contributed to the enhanced growth performance of the tilapia,
and the influence of BFT on enzyme activity varied between the liver
and intestine.