Effects of differently processed diets on growth,immunity and water quality of the sea cucumber,Apostichopus japonicus (Selenka, 1867)

The type of formulated diet used in aquaculture systems affects the feed efficiency and water quality. In this study, the water quality, growth performance and immunity of the sea cucumber, Apostichopus japonicus (Selenka, 1867), fed diets produced using four different processing methods (extruded pellet diet, cold‐bonded pellet diet, flake diet and mash diet) were quantified for 60 days to identify the optimal feed type for culturing of this species. Sea cucumbers grew faster, the feed conversion ratio was much lower, and immunity indicators were higher when fed the extruded pellet diet compared to the other diets. Sea cucumbers fed the extruded pellet diet had the highest specific growth rate (0.96), whereas A. japonicus fed the cold‐bonded pellet diet had the lowest specific growth rate (0.51). The lysozyme activity of sea cucumbers fed the extruded pellet diet was higher (57.52) than that of A. japonicus fed the cold‐bonded pellet diet (39.22), flake diet (37.32) and mash diet (32.68). When animals were fed the mash diet, the ammonia–nitrogen, nitrite–nitrogen and phosphate productions were higher than in animals fed the other diets. These results indicate that the extruded pellet diet is the optimum feed type for use in the culture of A. japonicus.     

Effect of replacing dietary fish meal with silkworm (Bombyx mori L) caterpillar meal on growth and non‐specific immunity of sea cucumber Apostichopus japonicus (Selenka)

The effect of dietary substitution of silkworm (Bombyx mori L) meal (SM) for fishmeal (FM) on the growth performance and non‐specific immunity of sea cucumber (Apostichopus japonicus) (initial weight: 12.8 ± 0.16 g) was determined. Four isonitrogenous and isocaloric diets were formulated: Diet 1, which served as the control diet, contained 5% FM; Diet 2 contained 3.75% FM and 1.25% SM; Diet 3 contained 2.5% FM and 2.5% SM; and Diet 4 contained 5% SM. Other ingredients in each of the four diets were kept in the same proportion. After 8 weeks of feeding, the results showed that sea cucumbers fed Diet 2 had 18.7% increases in weight over those fed the control diet, but no significant difference was observed. No obvious difference in body wall composition was detected among the sea cucumbers fed the four different diets. Immunity analysis indicated that phagocytosis and serum alkaline phosphatase activity were not significantly (P > 0.05) affected when FM was partially or completely replaced with SM. Serum lysozyme activity of sea cucumbers fed Diet 4 showed a significant (P < 0.05) growth increase compared with those fed control diet. The results revealed that SM could be an effective substitute for FM in sea cucumber diet.     

N and P budgets of Haliotis discus hanai,Apostichopus japonicas,and Sebastes schlegeli in a polyculture system

The viability of placing abalones (Haliotis discus hannai), sea cucumbers (Apostichopus japonicas) and rockfish (Sebastes schlegeli) in a polyculture system, the effect of this mixed species group on the system's nitrogen (N) and phosphorous (P) budgets, and the growth and food intake of the organisms in the system were examined using a recirculating aquaculture system. Four replicates were set up for each of three treatment groups (abalone only (C), abalone‐sea cucumber (AS) and abalone‐sea cucumber‐rockfish (ASF)) with an experimental period of 60 d. Compared with the C group, in the AS group the abalone survival rate and specific growth rate (SGR) of body weight increased and the harvested abalones from the polyculture system became the main source of N and P output of the polyculture system. However, the N and P output in the water layer did not differ significantly from that in the C group (p > 0.05), and the N utilization rate was significantly higher than that in the C and ASF groups (p < 0.05). Compared with the AS group, in the ASF treatment the SGR of body weight as well as the protease and amylase activities of sea cucumbers were significantly higher (p < 0.05), the water layer and faeces became the main sources of N and P output in the system. These results showed that the AS polyculture mode significantly improved the N and P utilization rates in the system and led to increased aquaculture production.     

Growth performance and digestion improvement of juvenile sea cucumber Apostichopus japonicus fed by solid‐state fermentation diet

In this study, the compound probiotics including Pseudoalteromonas. Sp D11, Bacillus subtilis A142, Saccharomyces cerevisiae Y23 and Lactobacillus plantarum L54 were applied for solid‐state fermenting the artificial diet of juvenile sea cucumber Apostichopus japonicus. The quality of solid‐state fermented (SSF) feed and its potential effects on growth performance and digestive enzyme activities were investigated. The results showed that, compared to unfermented diet, SSF feed had a better palatability quality; meanwhile, a higher ratio of crude protein, free amino acids and reducing sugars and a lower ratio of crude fibre, crude ash and alginic acid were found in SSF feed. The results of the feeding trial showed that feeding SSF feed could improve growth performance of sea cucumbers more than those fed with the unfermented diet. The results of digestive enzyme assays showed that feeding SSF feed to animals could significantly improve activities of amylase, cellulase, alginic acid enzyme and protease, which implied that fermented feed could improve digestibility of A. japonicus. In summary, the SSF feed fermented by compound probiotics had better palatability and nutrition value than unfermented feed. And feeding SSF feed could significantly improve the growth performance and digestion ability for sea cucumbers in the phases of nursery and grow‐out.     

Optimum Level of Dietary n‐3 Highly Unsaturated Fatty Acids for Juvenile Sea Cucumber,Apostichopus japonicus

A feeding trial was conducted to estimate the optimum level of dietary n‐3 highly unsaturated fatty acids (HUFAs) for juvenile sea cucumber, Apostichopus japonicas, based on growth performance and fatty acid compositions. Diets with five n‐3 HUFAs levels (0.15, 0.22, 0.33, 0.38, and 0.46%) were fed to sea cucumber juveniles (1.97 ± 0.01 g) once a day for 60 d. The sea cucumbers fed diets containing 0.22% n‐3 HUFAs showed significantly (P < 0.05) higher body weight gain, feed efficiency, and protein efficiency ratio than the sea cucumbers fed diets containing 0.15% n‐3 HUFAs, but not significantly different (P > 0.05) from those of sea cucumbers fed diets containing 0.33, 0.38, and 0.46% n‐3 HUFAs. The sea cucumbers fed diets containing 0.46% n‐3 HUFAs showed significantly (P < 0.05) higher eicosapentaenoic acid and saturated fatty acid than the sea cucumber fed diets containing 0.15% n‐3 HUFAs, but not significantly different (P > 0.05) from those of sea cucumbers fed diets containing 0.22, 0.33, and 0.38% n‐3 HUFAs. The results of growth performance and n‐3 HUFA compositions of body wall indicated that the optimum level of dietary n‐3 HUFAs for juvenile sea cucumber is between 0.22 and 0.46%.     

Dietary supplementation of red alga Pyropia spheroplasts on growth,feed utilization and body composition of sea cucumber,Apostichopus japonicus (Selenka)

A feeding experiment was conducted in a closed recirculating system to evaluate the effects of freeze‐dried spheroplasts prepared from Pyropia yezoensis (Ueda) on feed intake, growth and biochemical composition of sea cucumber, Apostichopus japonicus (Selenka). Pyropea spheroplasts (PS) were prepared through enzymatic treatment to break down the complex mixture of polysaccharides cell walls that might be easier for growth energy partitioning. Sea cucumbers were fed‐formulated diets with 10 (Diet 1), 30 (Diet 2) and 50 g/kg (Diet 3) inclusion level of PS. A diet without PS was used as a control (Diet 4). The experiment was conducted for 6 weeks maintaining water temperature 15 ± 1°C, photoperiod 18:06 hours (D:L). Feed was supplied ad‐libitum at 16.00 h once in a day, and the remaining feed and faeces were removed in the next day. Results showed that the highest growth was observed in the 50 g/kg PS diet compared to other treatments. Total weight gain, mean weight gain, net yield, protein efficiency ratio (PER) and protein gain (%) were significantly higher in the 50 g/kg PS diet (p < .05). A significantly higher percentage of energy was allocated for growth in the 50 g/kg PS diet. The highest specific growth rate and feed conversion efficiency (p < .05) were observed in the higher percentage of PS diet. Both the growth performance and biochemical analysis showed that superior growth was observed with increasing levels of PS in the diet. We infer that PS can be used as a new, cheaper feed ingredient in the formulated diet of A. japonicus.     

Effects of replacing fishmeal with fermented and non‐fermented rapeseed meal on the growth,immune and antioxidant responses of red sea bream (Pagrus major)

The effect of rapeseed meal (RM) and Aspergillus oryzae fermented rapeseed meal (RM‐Koji) on red sea bream (Pagrus major) was examined. Three groups of fish (initial weight, 4.5 ± 0.02 g) were fed a basal diet (RM0) and two test diets where half of fishmeal was replaced by RM (RM50) and RM‐Koji (FRM50) for 56 days. The obtained results showed that fish fed RM0 and FRM50 exerted significantly higher growth performance, feed utilization and haemoglobin level but lower triglyceride and cholesterol than RM50 group (p < 0.05). Interestingly, except of antiprotease activity, all the immune parameters including lysozyme, respiratory burst (NBT) and bactericidal activities were significantly increased in fish fed RM0 and FRM50 diets compared to RM50 diet (p < 0.05). In addition, malondialdehyde and reactive oxygen metabolites were significantly reduced in RM0 and FRM50 groups over RM50 group (p < 0.05). The present results suggest that fermented RM induced better growth performance and immune responses than feeding red sea bream with non‐fermented RM and both RM and RM‐Koji improved the antioxidative status of fish, making RM‐Koji an interesting candidate as a functional feed for aquatic animals.     

Effect of dietary carbohydrate levels on growth performance,non‐specific immune enzymes and acute response to low salinity and high temperature of juvenile sea cucumber Apostichopus japonicus

This study was performed to determine the optimum dietary carbohydrate (CHO) levels of sea cucumber, based on the parameters of growth, digestive enzymes, digestibility, non‐specific immune enzymes and acute low‐salinity (20 g/L) stress and high‐temperature (30°C) stress tolerance. Diets with eight different CHO (dextrin) levels (32.9, 107.6, 192.5, 257.2, 316.8, 428.0, 482.4 and 572.8 g/kg) were fed to sea cucumber juveniles (0.49 ± 0.01 g) for 60 days. Significant higher amylase activity was observed in sea cucumbers fed diet with CHO ranging between 32.9 and 192.5 g/kg than that of other treatments (p < .05). The sea cucumbers fed with 192.5 g/kg CHO showed significantly higher acid phosphatase activity than the treatments of 482.4 and 572.8 g/kg CHO (p < .05), and significantly higher alkaline phosphatase activity than other treatments (p < .05, except 257.2 g/kg). The treatments of 428.0–572.8 g/kg were found significantly lower values than other treatments in apparent digestibility coefficients for dry matter and crude protein (p < .05). The sea cucumbers fed with 192.5, 257.2 and 316.8 g/kg CHO showed better tolerance to high‐temperature (30°C) and low‐salinity (20 g/L) stress than other treatments. In brief, the optimal dietary CHO level for the growth of juvenile sea cucumber is 177.96 g/kg. However, excessive CHO will inhibit amylase enzyme activity and decrease digestibility, resulting in low growth of sea cucumber.     

Influence of Nitzschia sp. on release of nitrogen and phosphorus from sediment in pond breeding sea cucumbers

Due to the tonic and nutritive virtues of sea cucumbers, increased commercial aquaculture has resulted in the expansion of breeding ponds, a primary form of sea cucumber production. Expansion of such production methods has led to increased settling of organic wastes onto the seabed, resulting in enriched sediments. Nitzschia sp. serves as an edible sea cucumber feed. Release characteristics of nitrogen (N) and phosphorus (P) from sediments in the presence of different biomass densities of Nitzschia sp. were studied via laboratory static cultures. pH and dissolved oxygen (DO) in the overlying water and biochemical components (i.e., protein, chlorophyll a) of Nitzschia sp. were assessed. When the biomass of Nitzschia sp. was more than (2–5) × 10⁴ ind/cm², the release of N and P nutrients was significantly promoted; additionally, the DO content of the overlying water was relatively high and the pH was relatively stable, which favoured the accumulation of proteins and chlorophyll a in Nitzschia sp. The results indicated that Nitzschia sp. promotes the release of N and P in sediments while absorbing them to maintain their own growth and promote the accumulation of nutrients, such as proteins, for the sea cucumbers. At the same time, the algae release oxygen, increasing the DO of the overlying water, providing a healthy breeding environment for the sea cucumbers. Application of Nitzschia sp. has the potential to reduce environmental harm caused by sea cucumber cultivation and thus achieve sustainable aquaculture.     

Nitrogen and phosphorus budget of a Haliotis discus hannai and Apostichopus japonicus polyculture system

The system nitrogen (N), phosphorous (P) budget, N/P utilization rate and the physiological response mechanism of the abalone Haliotis discus hannai (body weight: 12.87 ± 0.82 g) and the sea cucumber Apostichopus japonicus (body weight: 10.85 ± 1.16 g) to different co‐culture environment conditions were examined. Animals were kept in a multilayer, cubic recirculating aquaculture system at different polyculture densities (abalones at 400 ind/m²in monoculture [Group C] and abalones at 400 ind/m²with sea cucumbers at 10 ind/m² [AS1] or 20 ind/m² [AS2]). Each treatment was replicated four times, and the experimental cycle was 90 days. No significant difference in survival rate of abalones was detected when the stocking density of sea cucumbers increased from 10 to 20 ind/m², but the concentrations of total ammonia nitrogen and nitrite nitrogen in the water were significantly higher in AS2 than in AS1. Survival rate, specific growth rate (SGR) of body weight of sea cucumbers and SGR of body weight of abalones were significantly lower in AS2 than in AS1. No significant difference in protease (PES), lipase, amylase and cellulase activities of abalones was identified between Group C and AS1, but the PES and amylase activities of abalones and sea cucumbers in AS1 were significantly higher than those in AS2. In AS1, the N/P output from harvesting of abalones and sea cucumbers and the N/P utilization rates were significantly higher than those in AS2. Although the N/P output from faeces was significantly lower in AS2 than in Group C and AS1, the N/P output from the water layer was significantly higher than that in AS1. The expression levels of Cu/Zn superoxide dismutase (Cu/Zn‐SOD) and heat shock protein 70 (HSP70) of both abalones and sea cucumbers in AS2 were significantly higher than those in AS1. No significant difference in expression of catalase (CAT) and HSP90of abalones was identified among these groups, but the expression levels of CAT and HSP90of sea cucumbers in AS2 were significantly higher than those in AS1. These results indicate that stocking sea cucumbers at 10 ind/m² in the polyculture system will relieve the organic load on the system and improve the N/P utilization rate. It will also increase aquaculture production and improve the ecological and economic benefits of the system.     

Effects of a probiotic mixture (Bacillus subtilis YB‐1 and Bacillus cereus YB‐2) on disease resistance and non‐specific immunity of sea cucumber,Apostichopus japonicus (Selenka)

The effect of a commercially available compound probiotics product containing Bacillus subtilis YB‐1 (50%) and Bacillus cereus YB‐2 (50%) fed to sea cucumbers, Apostichopus japonicus (Selenka) on challenge infections and non‐specific immune responses was assessed. Sea cucumbers (were randomly allocated into nine aquariums at a density of 30 sea cucumbers per tank and triplicate groups) were fed diets containing 0 (control), 10⁷ and 10¹⁰ cfu (g diet)^?1 of the probiotics mixture for 32 days. The growth factors and immunological parameters were measured. In addition, the effects on resistance against Vibrio alginolyticus infection were also evaluated. The results indicate that all the immunological parameters (phagocytic activity, superoxide anion production, lysozyme activity, catalase activity and phenoloxidase activity) measured and the growth rate of sea cucumbers fed 10¹⁰ cfu of the probiotics mixture were significantly (P < 0.05) improved than control groups at 16 and 32 days. After challenging, the cumulative mortality for the control was 100%, whereas the cumulative mortality for sea cucumbers fed 10¹⁰ cfu of the probiotics mixture was 47% (P < 0.05). Although the total autochthonous intestinal heterotrophic bacterial counts were not affected by dietary treatment (P > 0.05), Bacillus sp. levels were significantly elevated in sea cucumbers fed the probiotics mixture (P < 0.05). These results confirmed that administration of the probiotics mixture in the diet stimulated non‐specific immune responses and enhanced the growth performance of sea cucumbers, and was effective in controlling infections caused by V. alginolyticus.     

Feasibility of Offshore Co‐culture of Abalone,Haliotis discus hannai Ino,and Sea Cucumber,Apostichopus japonicus,in a Temperate Zone

Feasibility of offshore co‐culture of abalone and sea cucumber was investigated in Northern China. Survival and growth of abalone, Haliotis discus hannai Ino, and sea cucumber, Apostichopus japonicus, co‐cultured in abalone cages from suspended longlines, in the offshore area, were examined. Abalone and sea cucumbers were co‐cultured at density ratios of both 3:1 and 6:1 for 1 yr. Abalone were fed with fresh kelp and no additional feed was given to sea cucumbers. Survival of abalone and sea cucumber was 100% for all treatments. Abalone and sea cucumber grew well; the body weight (BW) of abalone and sea cucumber was nearly doubled and had reached a commercial size. There were no significant differences in the growth rates for both abalone and sea cucumber between the two density treatments. The specific growth rate of BW of abalone (SGRbw) was highest in June, with a value of 0.536%/d. Growth rate of sea cucumber (SGRsc) was highest in December, reached 1.84%/d, with an annual average SGRsc of 0.182%/d. Results suggested that the offshore co‐culture of abalone and sea cucumber was feasible offshore. The co‐culture of abalone with sea cucumbers may provide an additional valuable crop without additional financial input.     

Preliminary Study of the Optimum Dietary Ascorbic Acid Level in Sea Cucumber,Apostichopus japonicus (Selenka)

A 14‐wk feeding trial was carried out to evaluate the optimum dietary ascorbic acid (AA) level in juvenile sea cucumber, Apostichopus japonicus. Sea cucumbers averaging 1.49 ± 0.07 g (mean ± SD) were randomly distributed into 18 rectangular plastic tanks of 20 L capacity in a recirculating system (20 animals per tank). Six semipurified experimental diets were formulated to contain 0 (l ‐ascorbyl‐2‐monophosphate [AMP]; AMP0), 30 (AMP24), 60 (AMP48), 120 (AMP100), 240 (AMP206), and 1200 (AMP1045) mg AA/kg diet in the form of AMP using casein as the main protein source. Sea cucumbers were fed each of the six experimental diets in triplicate groups. At the end of 14 wk of feeding trial, weight gain (WG), specific growth rate (SGR), and feed efficiency (FE) of sea cucumbers fed AMP100, AMP206, and AMP1045 were significantly (P < 0.05) higher than those of animals fed AMP0, AMP24, and AMP48. However, there were no significant differences in WG, SGR, and FE among sea cucumbers fed AMP100, AMP206, and AMP1045 and among animals fed AMP0, AMP24, and AMP48. Whole‐body vitamin C concentration increased with AA content of the diets. Broken‐line analysis of WG showed an optimum dietary AA level of 105.3 mg AA/kg diet in sea cucumber. These results indicated that the optimum dietary vitamin C level in sea cucumber in the form of AMP could be greater than 100 mg AA/kg diet but less than 105.3 mg AA/kg diet.     

Improvement of growth performance,water quality and disease resistance against Vibrio harveyi of postlarval whiteleg shrimp (Litopenaeus vannamei) by administration of mixed microencapsulated Bacillus probiotics

The objective of this study was to investigate the effects of mixed Bacillus on growth, water quality and disease resistance against Vibrio harveyi in whiteleg shrimp (Litopenaeus vannamei). Postlarval shrimp (PL₃₀) were fed with (a) a basal diet (the control), (b) a diet containing mixed freeze‐dried Bacillus probiotics (FB) and (c) addition of mixed microencapsulated Bacillus probiotics (MB) in culture water. Addition of FB and MB probiotics improved (p < .05) growth, feed efficiency, survival and culture water quality (ammonia and nitrite) compared to the control group although there was no difference (p > .05) between the two treated groups. Bacillus numbers in gastrointestinal tracts and culture water of FB‐ and MB‐administrated shrimp were higher (p < .05) than in the control. After a 30‐day culture, shrimp were infected with V. harveyi and monitored for 10 days. A significant reduction (p < .05) in cumulative mortality was observed in FB‐ and MB‐supplemented shrimp (43.24% and 45.05%, respectively), compared to the control (63.06%). This finding demonstrated that administration of microencapsulated probiotics was as effective as freeze‐dried probiotics for improving growth, feed efficiency, survival, Bacillus in gastrointestinal tracts, water quality (ammonia and nitrite) and conferring disease resistance to V. harveyi.     

Formulated diet alters gut microbiota compositions in marine fish Nibea coibor and Nibea diacanthus

Nibea, an economical marine fish, is generally fed on trash fish (the low‐value fish), which can cause high feed costs and waste pollutions in high‐density aquaculture. To assess the effect of formulated diet on the gut microbiota in Nibea coibor and Nibea diacanthus, denaturing gradient gel electrophoresis, clone libraries analysis and Illumina sequencing of the 16S ribosomal RNA gene were used in this study. Two Nibea fishes were both dominated by Gammaproteobacteria (especially Photobacterium) and shared a set of gut microbiota, including Bacilli, Mollicutes, Alphaproteobacteria and Fusobacteriia. Statistical analyses revealed that formulated diet led to lower feed conversion ratio (p < 0.001), lower abundance of Vibrio (p = 0.040) and infectious diseases pathways (p = 0.001), higher abundance of polysaccharide‐degrading bacterium Cellvibrio (p = 0.006) in two Nibea species, with higher weight gain rate (p = 0.023) and microbial diversity (Shannon, p = 0.049 and Simpson, p = 0.044) and more carbohydrate metabolism (p = 0.020) observed in N. coibor. The distribution and correlation network of 17 potential short‐chain fatty acid producing bacteria were obtained and visualized in all treatment groups. The results reveal that formulated diet has beneficial effects on the gut microbial ecology in two Nibea fishes, which suggests the possibility of replacing trash fish diet with formulated diet in Nibea aquaculture.     

Effects of dietary protein levels on the activity of the digestive enzyme of albino and normal Apostichopus japonicus (Selenka)

We evaluated the effects of different proportions of dietary protein (5%, 10%, 15%, 20%, 25% and 30% protein) on the activity of digestive enzymes of normal and albino Apostichopus japonicus. The experimental diets were fed for 60 days, the optimal conditions for digestive enzyme activity in sea cucumbers were studied. The optimal temperature for protease was 29.3°C and the optimal pH was 1.8. The optimal temperature for amylase was 34.3°C and the optimal pH was 6.7. The optimal temperature for cellulase was 56°C and the optimal pH was 5.9. The activity of intestinal protease increased at first and then decreased as the proportion of dietary protein increased, reaching the maximum when the proportion of protein was 19.7%. The activity of protease in the intestine of normal sea cucumber was significantly lower than that of albino sea cucumber, and the activity of amylase was significantly higher than that of albino sea cucumber. This study is expected to provide a basis for further explaining the ecological difference of albino and normal A. japonicus.     

Effects of dietary supplementation with β‐glucan and synbiotics on growth,haemolymph chemistry,and intestinal microbiota and morphology in the Pacific white shrimp

The goal of this study was to investigate the effects of dietary supplementation with β‐glucan and microencapsulated probiotics (Bacillus subtilis or Pediococcus acidilactici) on growth performance, body composition, haemolymph constituents, and intestinal morphology and microbiota of the Pacific white shrimp Litopenaeus vannamei. Four treatment diets [basal diet (C), β‐glucan‐containing diet (β‐glu), β‐glucan plus B. subtilis‐containing diet (β‐glu+Bs), and β‐glucan plus P. acidilactici‐containing diet (β‐glu+Pa)] were fed to L. vannamei for 90 days. Shrimp fed the β‐glu and β‐glu+Pa diets exhibited similar growth performance and body protein content, which were significantly higher than those of shrimp fed the control diet (P < 0.05). No significant differences in haemolymph triglyceride, cholesterol, protein, haemolymph urea nitrogen or chloride were detected among the experimental diets. However, dietary β‐glucan alone increased the haemolymph glucose level and osmolarity (P < 0.05). Synbiotic supplementation had greater effects on intestinal microbiota and morphology than dietary β‐glucan alone. For example, β‐glu+Bs increased the number of intestinal lactic acid bacteria and decreased the number of Vibrio spp. (P < 0.05), and β‐glu+Pa increased the height of intestinal villi.     

Effects of Jerusalem artichoke powder on the growth performance,nonspecific immunity,and gastrointestinal microbiota of sea cucumber

This study investigated how Jerusalem artichoke powder (JAP) affected the growth, immunity, and gut microbiota of the sea cucumber, Apostichopus japonicus Selenka. Animals were fed diets containing antibiotic (1 ppm) or five levels of JAP (0, 2.5, 5, 10, and 15 g/kg). After the feeding trial, three sea cucumbers were sampled per tank to assay for immunity and gut microbiota composition. Dietary supplementation of 2.5 g/kg JAP significantly improved the growth rate and phenoloxidase activity of sea cucumbers. The diet containing 5 g/kg of JAP increased the survival rate and phagocytic activity, and the diet containing 15 g/kg of JAP increased the growth rate and total coelomocyte count of sea cucumbers. Moreover, exposure to antibiotics significantly changed the microbiota of sea cucumbers, while the JAP supplementation stimulated the development of microbiota communities, which could be more homogeneous. Supplementing the diets with 15 g/kg of JAP increased the growth of Rhodobacterales, and this may underlie the higher growth rate of sea cucumbers in this treatment. Considered together, our results suggest that supplementing the diet of sea cucumber with JAP may be beneficial for nonantibiotic farming of sea cucumber.     

Effects of Dietary Taurine on the Growth,Digestive Enzymes,and Antioxidant Capacity in Juvenile Sea Cucumber,Apostichopus japonicus

Taurine has been widely used as a growth‐ or health‐promoting additive in aquatic animals because of its multiple functions, while little work has been done on its effects on sea cucumbers, in spite of the occurrence of serious diseases. In this study, juvenile sea cucumbers (4.68 ± 0.04 g) were fed diets supplemented with taurine at 0% (control), 0.1, 0.25, 0.5, 1, and 2% for 8 wk. At the end of an 8‐wk feeding trial, growth performance of sea cucumbers was not significantly affected by dietary taurine (P > 0.05). However, dietary taurine significantly elevated intestinal lipase activities of sea cucumbers (P < 0.05). Intestinal amylase activity and trypsin activity in sea cucumbers did not show significant changes after animals were fed diets supplemented with taurine (P > 0.05). Dietary taurine at all five dosages significantly increased total antioxidant capacity in sea cucumbers, while superoxide dismutase activity in groups with dietary taurine at 0.25 and 0.5% was significantly higher than that of the control group (P < 0.05). Therefore, it appears that taurine could be used as a potential feed additive to confer better health of farmed sea cucumbers.