Utilization of dietary carbohydrates by sea cucumber Apostichopus japonicus (Selenka) as indicated by carbon stable isotope analysis

Carbon stable isotopes were used as trophic markers to investigate the utilization of dietary terrestrial‐source carbohydrates by sea cucumber Apostichopus japonicus. Sea cucumbers were fed by five different types of diets with the ingredients containing Sargassum muticum either without starch or with one of the four starches including corn starch, sweet potato starch, tapioca starch and potato starch. After the 70‐day feeding trial, the carbon isotopic compositions of A. japonicus appeared to reflect those of corresponding dietary components. The average contribution of corn starch (22.0%) to the growth of A. japonicus was slightly higher than the expected contribution (20%). While the proportional contributions of sweet potato, tapioca and potato starches (6.0%, 7.0% and 4.0%, respectively) were all considerably lower relative to the expected contributions. These results indicated that A. japonicus could utilize corn starch more efficiently than sweet potato, tapioca or potato starch. Moreover, A. japonicus fed diet containing corn starch showed the highest specific growth rates which were significantly higher than those fed diets containing potato or tapioca starch. The results of the present study suggested that the corn starch could be used as dietary carbohydrate source in the artificial feeds for A. japonicus farming.     

Requirement of vitamin E of growing sea cucumber Apostichopus japonicus Selenka

This feeding trial was conducted to determine the vitamin E requirement of growing sea cucumber Apostichopus japonicus Selenka. Six isonitrogenous and isoenergetic experimental diets were formulated to contain graded levels of vitamin E (6.7, 81.2, 159.3, 237.8, 314.6, 395.9 mg/kg diet). Each diet was assigned randomly to 30 growing sea cucumber with initial body weight 15.43 g in triplicates for 8 weeks. Survival rate was not affected by dietary vitamin E; meanwhile, both the weight gain (WG) and specific growth rate were presented the trend of increasing first and then kept stable. With the increasing of dietary vitamin E, crude lipid content of body wall was evaluated firstly and dropped afterwards. When dietary vitamin E contents were lower than 159.3 mg/kg, vitamin E contents of body wall were increased by dietary vitamin E levels, but there were no more differences when dietary vitamin E higher than 159.3 mg/kg. There were minor effects on digestive enzymes of intestine by dietary vitamin E. Contents of malondialdehyde were decreased, while the total superoxide dismutase activity was increased first and then decreased with the increasing of dietary vitamin E. Activities of intestinal alkaline phosphatase were increased, and glutamic oxaloacetic transaminase were decreased first and then increased with the increasing of dietary vitamin E. In conclusion, analysis by a linear regression equation of WG or vitamin E contents in body wall indicated that the optimum requirement of vitamin E for growing sea cucumber (initial body weight 15.43 g) was 165.2–187.2 mg/kg diet.     

Effects of dietary protein levels on the growth,body composition,serum biochemistry and digestive enzyme activity in Chinese rice field eel (Monopterus albus) fingerlings

A 12‐week feeding trial was conducted to determine the influence of dietary protein levels on growth performance, body composition, haematological parameters and digestive enzyme activity of Chinese rice field eel (Monopterus albus) fingerlings. Six isolipidic experimental diets (27.89%, 32.23%, 35.95%, 40.06%, 43.31% and 46.53%) were formulated to randomly assign to triplicate groups of 50 rice field eel fingerlings (5.0 ± 0.5 g) cultured in plastic cages. Results indicated that the best growth performance of fish with the highest WG (158.68 ± 31.59%) and SGR (2.28 ± 0.21%) was obtained at 40.06% group. Significant alterations were demonstrated on whole‐body crude protein, crude lipid and amino acid profile by different dietary protein levels. Besides, haematological parameters including triacylglycerol, aspartate aminotransferase and alkaline phosphatase decreased with various levels by the increasing of dietary protein levels. The lowest pepsin activity was observed in 27.89% protein group, which suggested lower availability of protein as substrate for protease activity. Meanwhile, the highest amylase activity in fish of 27.89% group indicated higher carbohydrate level in this group. Based on the polynomial regression analysis of WG and SGR, the dietary protein requirement for fingerlings of Monopterus albus was estimated to be 386.4–390.8 g/kg, respectively, with the lipid level of 10.08%.     

Effects of diatom concentration in prepared feeds on growth and energy budget of the sea cucumber Apostichopus japonicus (Selenka)

Eight test diets were used in the experiment: seven fresh diatom (Cylindrotheca fusiformis) diets in which diatom occupied 100%, 83.3%, 50%, 33.3%, 20%, 14.3% and 11.1% in dry matter of the feeds (marked as D100, D83, D50, D33, D20, D14 and D11), and a formulated diet (70% Sargassum thunbergii powder, 20% sea mud and 10% fish meal, based on dry weight, marked as ST). The results showed that the specific growth rates (SGRs) of the animals fed diets D33, D20, D14 and D11 were not significantly different from the SGR of those fed diet ST. However, the energy allocated to growth for the animals fed with diet D14 was twice that of diet ST. For sea cucumbers fed diet D14 the largest expenditure part was allocated to respiration (55.4%), but for those fed diet ST, the largest part was allocated to faeces (62.7%). The organic content of diet D14 was also much lower than that of diet ST. Frozen diatom diets containing 14% (dry matter weight) fresh diatom could be an environmentally friendly feed as an alternative option for macroalgae powder.     

Effects of dietary peptide intake on growth,energy budget,body composition and non‐specific immunity of the sea cucumber Apostichopus japonicus (Selenka)

In this study, a 60‐day feeding trial was conducted to determine the effects of feed supplementating the feed of Apostichopus japonicus with peptides on its growth, energy budget, body composition and immune responses. Sea cucumbers were fed with five experimental diets supplemented with different proportions of peptides: 0 (D1), 12.5 (D2), 25 (D3), 37.5 (D4) and 50 (D5) g/kg in basal diet. Our results suggested that specific growth rate (SGR) and ratio of viscera to body wall (RVBW) of sea cucumbers fed with D4 were significantly improved. Relative to D1, ingestion rate (IR) and faeces production rate (FPR) for D3 and D4 were reduced considerably. Notably, the energy intake increased when peptide level increased from 0 to 50 g/kg. Meanwhile, the energy deposited for growth increased, and the energy loss decreased when peptide level increased from 0 to 37.5 g/kg. The sea cucumbers in D4 had the highest level of crude fat and lowest crude ash. The activities of immunoenzyme, such as SOD, CAT, T‐AOC, ACP and AKP, increased with peptide increase. Results suggested that supplementation of the feed with 25–37.5 g/kg peptides could significantly improve the growth performance, body composition and immune capacity of Apostichopus 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.     

Effect of temperature on growth,digestion and immunity of green,white and purple sea cucumbers,Apostichopus japonicus (Selenka)

Three color morphs (white, green and purple strains) of Apostichopus japonicus (Selenka) were cultured in artificial seawater, for approximately 90 days, in three temperature ranges: 27–22°C (high), 22–17°C (mid) and 17–12°C (low). All strains grew in all temperature ranges. Temperature significantly affected growth rate, digestibility, digestive enzymes and immune‐related enzymes. Highest specific growth rates were exhibited in 4‐month‐old sea cucumbers at mid and high temperatures, and in 16‐month‐old sea cucumbers at mid and low temperatures. Specific growth rates of green and purple strains were not significantly different, but were significantly higher than that of the white strain at mid temperatures. The digestibility of each strain was significantly higher at 27°C, 22°C and 17°C than at 12°C. Green‐strain digestibility was higher than that of purple and white strains at specific temperatures. Protease and amylase activities of all strains followed bell‐shaped temperature curves with maximum digestive enzyme activity at 17°C. The activities of alkaline and acid phosphatases were higher in the guts of the green strain than in the white or purple strains at the same temperature. Superoxide dismutase activity was higher in the purple strain than in white and green strains.     

A preliminary identification of genomic loci for body colour variation in the sea cucumber Apostichopus japonicus

The sea cucumber Apostichopus japonicus is one of the most economically important aquaculture species in China, which shows a distinct characteristic of body colour variation. A number of purple variants were obtained in the coast of China, which shows great potential to develop a niche market. In the present study, to understand the genetic basis of green‐purple colour variation, a genome‐wide association study based on the 2b‐RAD sequencing was conducted. As a result, 8,795 genome‐wide single nucleotide polymorphism (SNP) markers were obtained and then applied to the association analysis. Ten most associated SNP loci with p‐value <1.0 × 10^–8 were obtained, and they were assigned to 4 chromosomes (chr17, chr21, chr15 and chr05). In genomic regions neighbouring to those SNPs, 33 candidate genes with annotation were obtained and the endothelin‐converting enzyme‐1, which was reported to be involved in pigmentation variation, was identified. To our knowledge, this is the first report of the genetic locus for body colour variation in this species. These findings will be useful for the fine mapping of the determining gene for body colour variation of A. japonicus.     

Effects of kelp residues fermented with probiotics on the culture of sea cucumber,Apostichopus japonicus

The kelp aquaculture production in China is the largest in the world, and a large amount of kelp residue is produced by kelp processing. Kelp residues contain substantial quantities of crude fibre, protein, and residual alginic acid, and may be used as feedstuff for aquaculture animals. In this study, we used probiotics to ferment kelp residues to improve kelp nutrient content and then fed the fermented kelp to the sea cucumber, Apostichopus japonicus. To study the effect of fermented feed on sea cucumber, its growth performance, digestive enzyme activity, diversity of intestinal microbiota and water quality of the sea cucumber culture water were determined. Growth performance of sea cucumber fed with fermented feed significantly (p < .01) increased when compared with sea cucumber fed with formulated feed. Amylase, cellulose and alginase activities were significantly (p < .01) higher in the fermented feed group when compared with the formulated feed group. The total number and diversity of intestinal microbiota showed a significant increase in sea cucumbers fed with the fermented feed. The water quality of the fermented feed group showed much lower ammonia and nitrite (<0.050 mg/L) levels when compared with the formulated feed group. These results suggest that kelp residues fermented with probiotics enhance the growth, digestive enzyme activities and intestinal microbiota of sea cucumbers and improve the culture water quality. Fermented kelp residues are a new supplementary nutrient source for sea cucumbers and may be applicable to other animal aquacultures.     

食源色氨酸添加量对不同密度下刺参生长和代谢酶活性的影响

为研究食源色氨酸添加量对不同密度下刺参生长和代谢酶活性的影响,在水温(17±0. 5)℃下将初始体质量(湿重)为(3. 5±0. 1) g的刺参(Apostichopus japonicus Selenka)饲养在40 L(53 cm×28 cm×34 cm)的玻璃水族箱中,密度分别为4(L组)、8(ML组)、16(MH组)和32(H组)头/40 L,分别投喂添加0%、1%、3%和5%色氨酸的饲料,饲养75 d,每个处理组设4个重复。试验测定了刺参体质量变化和代谢酶活性,结果显示:随着养殖密度增加,刺参生物量增加,刺参增重率下降。最大生物量为196. 1 g(3%色氨酸,H组),最低增重率为35. 9%(5%色氨酸,H组);与对照组相比,饲料中添加3%色氨酸处理组刺参生长更快;在各养殖密度下,添加3%色氨酸处理组的谷丙转氨酶(ALT)、谷草转氨酶(AST)、乳酸脱氢酶(MDH)和苹果酸脱氢酶(LDH)酶活力低于其他处理组。高密度(H组)下,添加3%色氨酸处理组的ALT、AST、MDH和LDH活力分别为5. 56 U/g prot、1. 85 U/g prot、0. 17 U/mg prot、64 U/g prot,低于对照组。研究表明,添加1%～3%食源色氨酸可以缓解高密度养殖对刺参的胁迫,提高刺参生长率。     

Spontaneous captive breeding and larval development in the green and red variants of the Japanese sea cucumber Apostichopus japonicus (Selenka 1867)

We report the spontaneous spawning, larval development, survival rate and larval growth rate patterns observed in the green and red variants of the Japanese sea cucumber Apostichopus japonicus. The green variant adapted well to the captive conditions in the Sasebo City Fisheries Center and spontaneously spawned without any induction or stimulation. One hundred individual green variants spawned nine times and produced approximately 155 million eggs. In contrast, 50 individual red variants showed poor adaptation to captivity and spawned spontaneously only three times, producing about 12 million eggs. Larval development and growth rate pattern was almost identical between the two variants of A. japonicus. In contrast, the larval survival rate for the green variant was over 90% up to the auricularia stage (10 days), but much low (less than 30%) for the red variant. We demonstrated that the green variant of A. japonicus was easier to rear in captivity. This provides a useful method for maintaining sustainable harvests and eventually contributing to restocking and sea ranching of the existing population. Further studies about optimal ecological conditions and behaviour are needed to improve egg production and survival rate of the red variant of A. japonicus.     

Effects of dietary protein to energy ratios on growth,body composition and digestive enzyme activities in Chinese mitten‐handed crab,Eriocheir sinensis

This study aimed to determine the optimal protein to energy ratio (P/E ratio) and evaluate the effect of dietary protein and lipid levels on growth performance, body composition and digestive enzymes activities in Chinese mitten‐handed crab, Eriocheir sinensis. Nine practical diets containing three levels both for protein (DP 30%, 35% and 40%) and lipid (DL 2%, 7% and 12%) with P/E ratios ranging from 13.69 to 19.79 mg KJ^?1 were fed to four replicates of crabs (3.39 ± 0.10 g) for 10 weeks. Weight gain increased significantly with the increase in DP level at each DL level. Moreover, weight gain increased in crabs fed with diets containing DL level from 2% to 12% and DP level from 30% to 35%. However, the diet containing 40% DP and 12% DL levels significantly decreased the growth performance and protein efficiency of the crabs. The whole crab and hepatopancreas lipid contents also increased as dietary lipid increased, but not dietary protein. The total protease activity increased significantly with the increase in dietary protein at each lipid level. The lipase activity was statistically comparable among different DL levels at each DP level. Taken together, the crab fed the diet containing 35% protein and 12% lipid levels with P/E 15.77 mg KJ^?1 revealed optimal growth, feed utilization efficiency and digestive enzymes activities. Moreover, our study indicated that the higher dietary lipid level at a relatively lower dietary protein level could provide protein sparing effect in Eriocheir sinensis.     

Effects of dietary macroalgae meal and lipid source on growth performance and body wall fatty acid composition of sea cucumber Apostichopus japonicus

A 70‐day experiment was conducted to examine the effects of different macroalgal meals and lipid sources on growth, body wall composition and fatty acid (FA) profile of sea cucumber Apostichopus japonicus. Two macroalgal meals including Sargassum muticum (SM) and Gracilaria lemaneiformis (GL) and two lipid sources including fish oil (FO) and vegetable oil (VO) were formulated into four diets, i.e., S. muticum and fish oil (SF), S. muticum and vegetable oil (SV), G. lemaneiformis and fish oil (GF) and G. lemaneiformis and vegetable oil (GV). The results showed that the specific growth rates (SGR) of A. japonicus fed diets containing SM were significantly higher than those fed diets containing GL. No significant differences in SGR between the FO‐based and VO‐based groups were observed. Similar results were observed in the body wall lipid content. Most body wall FAs changed to resemble the dietary FA proportions because of the dietary effect. Concentrations of 20:4n‐6 of the SF and GF groups were significantly lower than the SV and GV groups, while levels of 20:5n‐3 and 22:6n‐3 were significantly higher than the SV and GV groups. The n‐3/n‐6 polyunsaturated fatty acids (PUFA) ratios of the SF and GF groups were significantly higher than the SV and GV groups. Moreover, the SF group had significantly higher 20:5n‐3 and 22:6n‐3 contents and n‐3/n‐6 PUFAs ratio than the GF group. These findings reveal that the SF diet can show beneficial effects on both growth performance and body wall n‐3 PUFAs content of A. japonicus.     

Effects of l‐tryptophan on the performance,energy partitioning and endocrine response of Japanese sea cucumber (Apostichopus japonicus Selenka) exposed to crowding stress

The effects of dietary tryptophan on growth performance, energy budget and endocrine response of sea cucumber Apostichopus japonicus (Selenka) were studied, to test whether the tryptophan could mitigate the crowding stress response of the sea cucumber. Four density treatments of the sea cucumber (i.e. 4, 8, 16 and 32 individuals per 40 L water, represented as L, ML, MH and H) were fed with diets containing 0 (control), 1%, 3% and 5% l ‐tryptophan, respectively, for 75 days. The results showed that the specific growth rate (SGR) and feed conversion ratio (FCE) of A. japonicus decreased with increasing in the stocking densities but increased after supplementation of 1% and 3% tryptophan. The energy allocation of the A. japonicus was affected significantly by stocking density and dietary tryptophan treatments (p < .05). In general, the energy consumed (C) and energy used for growth (G) decreased with the increasing in the stocking densities. The highest proportion of energy deposited to growth occurred in each 3% treatment (L, 6.38%; ML, 6.12%; MH, 4.56% and H, 4.14%), which were significantly higher than the controls (p < .05) respectively. Higher cortisol, glucose and lactate levels of A. japonicus were recorded in the control treatments of MH and H, but l ‐tryptophan supplementation could reduce the levels of cortisol, glucose and lactate of the test animals. The present results proved that the growth performance of the sea cucumber was inhibited by high stocking densities, while dietary supplementation of tryptophan could significantly mitigate the crowding stress, and improve the growth of sea cucumber.     

Effects of stocking density and body physical contact on growth of sea cucumber,Apostichopus japonicus

The present study was conducted to investigate the effects of physical contact on the growth of Apostichopus japonicus through various stocking densities, group culture and physical isolation culture. The results showed that the specific growth rates (SGR), the feed conversion efficiencies and the energy used for growth of the animal decreased with the increase in stocking density, while the coefficient of variations (CV) in group culture treatments increased. In high density treatments (4, 6 ind./40 L), the SGRs in isolated culture treatments were not different to those in group culture treatments of the same density, however, the CVs in the latter (58.0% and 60.4%, respectively) were significantly higher than those in the former (37.8% and 35.8%, respectively). The CV difference between group one and isolated one of the same density (20.2% and 24.7%, respectively) was less than that in single individual culture (32.7%), indicating that the effect of physical contact on growth variation was weaker than that of genetic factor. This study proved that the individual growth variation in sea cucumber resulted mainly from genetic factor and physical contact, while some chemical mediator might also be the factor affecting the growth rate of sea cucumber.     

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.     

Microbial communities in sea cucumber (Apostichopus japonicus) culture pond and the effects of environmental factors

This study investigated microbial community composition as well as their correlation with environmental factors of Apostichopus japonicus culture ponds in northern China by 16S rRNA gene amplicon sequencing. The results showed that microbiota richness varied consistently with diversity in the pond ecosystem. Microbiota richness and diversity were highest in sediment, followed by gut of A. japonicus and water. The dominant bacterial phylum in the pond ecosystem is Proteobacteria. Gammaproteobacteriaeria and Flavobacteria are two dominant bacterial classes in the ecosystem. There is significant difference (p < 0.05) between dominant bacterial communities at the levels of order, family and genus. There is also remarkable regional difference (p < 0.05) between microbial community composition in the pond ecosystems. Specifically, microbial community composition in Changhai and Yingkou show a high similarity, so do those of Laoting and Rushan. According to the redundancy analysis of the microbial community composition and pond environmental factors, chemical oxygen demand is the dominant environmental factor determining microbial community composition in pond water; sulphide has the greatest influence on the microbial community composition in pond sediment; the rest of environmental factors have varied influence on microbial community composition in pond ecosystems.     

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 garlic powder on feeding attraction activity,growth and digestive enzyme activities of Japanese seabass,Lateolabrax japonicus

The study was to investigate the effects of garlic (Allium sativum) powder on feeding attraction activity, growth performance and digestive enzymes of juvenile Japanese seabass, Lateolabrax japonicus (initial weight: 29.82 ± 0.24 g). Six concentration gradients (0, 5, 10, 15, 20 and 25 g/kg diets) were formulated for luring and feeding experiment. The results showed a clear attractive trend of garlic powder for L. japonicus. A 28‐day feeding experiment indicated garlic could reduce the feed conversion ratio (FCR) (p < .05). The content of the body crude lipid was significantly increased at 10–15 g/kg diet (p < .05). Digestive enzyme activities including trypsin, amylase (AMS) and lipase (LPS) in the intestine were the highest at 10 g/kg diet (p < .05). Overall, garlic powder provides a promising and effective method for Japanese seabass healthy culture by improving fish growth and digestive ability. The results of this research suggested the additive suitable dosage of garlic powder was about 10 g/kg diet.     

饲料蛋白水平对方格星虫稚虫日增重和消化酶活性的影响

为探讨饲料蛋白水平对方格星虫稚虫日增重和消化酶活性的影响,以9种蛋白水平(25.21%、29.87%、35.03%、40.67%、45.47%、50.12%、55.29%、60.38%、64.85%)的等能微颗粒饲料(以D1-D9表示)饲喂稚星虫8周。结果表明,饲料蛋白水平对稚星虫的日增重有显著影响(P<0.05)。随着饲料蛋白水平的提高,稚星虫的日增重呈先增后降的趋势,在D5组达到最大值。对稚星虫消化酶活性的分析表明,稚星虫蛋白酶活性随着饲料蛋白水平的上升呈先增后降的趋势,在D6组达到最大值,且显著高于D1-D5组(P<0.05);淀粉酶和脂肪酶活性随着饲料蛋白水平的上升有显著降低的趋势(P<0.05),D9组稚星虫的淀粉酶活性显著低于D1-D4组(P<0.05);D9组稚星虫脂肪酶活性显著低于除D8组外的其他各蛋白水平组(P<0.05)。以日增重为评价指标,稚星虫对饲料蛋白的适宜需求量为46.69%。