In order to understand enzymatic alteration during the restricted-to-fed feeding schedules in cycles, the modulation of key enzyme activities in digestion was studied in different part of gastrointestinal track of juvenile gilthead sea bream (Sparus aurata). Juveniles (6.4 g) were stocked into 12 tanks at a density of 16 fish per tank. Four different feeding schedules were tested on triplicate groups of juvenile fish: (1) fish were fed to apparent satiation twice a day throughout 48 days, (2) starvation for 1 day and then re-fed for 2 days (S1), (3) 50% satiation for 2 days and then re-fed to apparent satiation for 2 days (R2), (4) 50% satiation for 6 days and then re-fed to apparent satiation for another 6 days (R6). The activity total protease, amylase and lipase in the control group were higher than those S1 and R6 in whole gastrointestinal track. The restricted feeding in R2 enhanced the activities of lipase, amylase, and, to some extent, total protease in fish, with the most pronounced effect exhibited in the pyloric caeca. Generally, total protease and lipase activity of fish in R2 exhibited no significant difference compared to the control, except amylase activity in mid-intestine. Thus, because of preserved digestive enzyme activities, some food restriction (R2) cycles may be recommended as a routine procedure in commercial production of juvenile gilthead sea bream.

In order to understand enzymatic alteration during the restricted-to-fed feeding schedules in cycles, the modulation of key enzyme activities in digestion was studied in different part of gastrointestinal track of juvenile gilthead sea bream (Sparus aurata). Juveniles (6.4 g) were stocked into 12 tanks at a density of 16 fish per tank. Four different feeding schedules were tested on triplicate groups of juvenile fish: (1) fish were fed to apparent satiation twice a day throughout 48 days, (2) starvation for 1 day and then re-fed for 2 days (S1), (3) 50% satiation for 2 days and then re-fed to apparent satiation for 2 days (R2), (4) 50% satiation for 6 days and then re-fed to apparent satiation for another 6 days (R6). The activity total protease, amylase and lipase in the control group were higher than those S1 and R6 in whole gastrointestinal track. The restricted feeding in R2 enhanced the activities of lipase, amylase, and, to some extent, total protease in fish, with the most pronounced effect exhibited in the pyloric caeca. Generally, total protease and lipase activity of fish in R2 exhibited no significant difference compared to the control, except amylase activity in mid-intestine. Thus, because of preserved digestive enzyme activities, some food restriction (R2) cycles may be recommended as a routine procedure in commercial production of juvenile gilthead sea bream.