Postprandial Changes in Digesta, Leftovers and Feces, and Their Carbon and Nitrogen contents in Cultured Red Sea Breams, Pagrus major

Abstract

For establishing a sustainable aquaculture for red sea bream, we examined postprandial changes in digesta and suspending matter discharged as leftovers and feces. Gastral digestion for extruded pellet (EP) needed 24 h in the fish weighing 158 g at water temperature rage of 20.3 - 26.6°C. Enteral digestion for EP almost ceased at about 72 h after feeding. The C/N ratio of suspending matter was similar to EP until 3h after feeding, and rapidly rose after then. This suggested that suspending matter until 3h after feeding and after then was originated from leftovers and feces, respectively. EP given was discharged as leftovers and feces ranges of 3.6-15.4 and 4.1-14.7%, respectively. Moist pellet (MP) given was also discharged as leftovers and feces ranges of 10.1-19.2 and 2.6 -10.8%, respectively. Feed intake, leftovers and feces of MP were 1.9, 3.5 and 1.5 times greater than those of EP, respectively. Until 3h after feeding EP, N in leftovers was at the range of 48.3-57.4% of total N discharged. Therefore, it is intensely recommended that preferable feeding restriction with EP is effective for conducting nitrogen load reduction and sustainable aquaculture for red sea bream.