Abstract:To explore the potential of fermented feed in sea cucumber cultivation, the effects of fermented feed on the energy budget, growth, non-specific immune enzymes, and digestive enzyme activities of sea cucumber (Apostichopus japonicus) seedlings were measured, and changes in water quality (including ammonia nitrogen, nitrite, and pH) in the culture ponds during a 7-day substrate change period were measured. The results showed that during the 50 day experimental period, the survival rate of the fermented feed group was (91.51±0.74)%, which was significantly higher than that of the unfermented feed group [(82.35±2.22)%] (P<0.05), and there was no significant difference between the two groups for specific growth rate. The growth energy ratio and metabolic energy ratio of the fermented feed group was (13.25±1.01)% and (32.32±2.00)%, respectively, whereas the values in the unfermented feed group were (11.38±1.05)% and (44.12±0.54)%, respectively; therefore, the fermented feed enhanced the growth energy of the seedlings. For the nonspecific immune-enzyme and digestive activities fed the different types of feed, the alkaline phosphatase, lysozyme, and pancreatic enzyme activity of the fermented feed group was (0.74±0.04) king U/100 ml, (95.52±14.80) U/ml, and (335.89±13.01) U/mg prot, respectively, which was significantly higher than that of the unfermented feed group (P<0.05). The concentration of ammonia nitrogen and nitrite on the 7th day of the substrate change period in the fermented feed group reached (263.27±32.57) µg/L and (315.15±61.41) µg/L, respectively. The values in the unfermented feed group were (462.86±14.69) µg/L and (572.87±25.75) µg/L, respectively, which were significantly higher than that of the fermented feed group (P<0.05). All the results showed that the fermented feed improved the physiological metabolism level of the sea cucumber seedlings and maintained the water quality of the culture system; therefore, fermented feed has a broad application prospect for sea cucumber seedling culture.
