3.5. Fish welfare
In the current study, there was no significant difference in the ALP,
LYZ, or T-SOD activity (P N 0.05) in the hepatopancreases or head
kidneys of the fish cultured in BFT and the RAS at the end of the exper-
iment. Moreover, no significant differences in the LYZ activity in the he-
patopancreas, serum ALP activity, and serum glucose concentrations
were found in the fish from BFT and the RAS (P N 0.05). However, the
serumT-SOD concentration in the fish cultured in BFTwas substantially
higher than that in the fish cultured in the RAS (Table 4). SODs are a
group of metalloenzymes that play a key role in the defense against
the toxic effects of reactive oxygen species and can be useful
for assessing oxidative stress (Lenartova et al., 1997; Pedrajas et al.,
1998). In the current study, the tilapia cultured in BFT tanks exhibited
superior T-SOD activity, indicating that feeding on biofloc improved
the immunity of the tilapia; this finding is consistent with the results
of the growth performance and digestive activity analysis.