Effects of dietary Ampithoe sp. supplementation on the growth, energy status, antioxidant capacity, and ammonia-N tolerance of the shrimp Litopenaeus vannamei: Continuous versus interval feeding

A 48-day feeding trial and an acute ammonia-N stress test were performed to investigate the effects on the growth performance, energy status, antioxidant status, and ammonia-N tolerance of Litopenaeus vannamei (5.0 +/- 0.2 cm, 1.6 +/- 0.4 g) when commercial feed was supplemented with freeze-dried powder of Ampithoe sp. (FDPA) on an interval and a continuous schedule. Shrimp fed with commercial feed were defined as the control group. For the interval feeding group (INF group), commercial feed supplemented with FDPA was provided once every 4 days, while commercial feed was used on the remaining days. The continuous feeding group (COF group) received commercial feed with added FDPA every day. The shrimp in the INF group and COF group showed better growth performance than did the control shrimp, and the survival rate and average yield in the COF group were significantly higher than those in the control group. During the culture period, the concentrations of glucose, triglycerides and total cholesterol in the hemolymph of shrimp were generally higher in the INF and COF groups than in the control group, and the concentrations in the COF group were generally higher than those in the INF group. Compared with the control group, shrimp in the INF and COF groups had elevated glutathione peroxidase (GSH-Px) activity, total antioxidant capacity (T-AOC), and expression levels of ATPase-a and PFK in the hemolymph or hepatopancreas, along with reduced malondialdehyde (MDA) concentrations and expressions of AMPK-alpha and FAS in the hepatopancreas. At 48 to 192 h during the ammonia-N stress test, the concentrations of urea-N and ammonia-N in the hemolymph generally remained lower in the INF group and COF groups than in the control group. At the end of the ammonia-N stress test, the shrimp mortality rates in the INF and COF groups were 28.1% and 40.6%, respectively, which were lower than the rate of 75.0% observed in the control group. In conclusion, dietary supplementation with FDPA had a positive influence on shrimp growth performance, energy status, antioxidant status and ammonia-N tolerance, and continuous feeding appeared to be more effective than interval feeding at improving antioxidant capacity.