Change of digestive physiology in sea cucumber <Emphasis Type="Italic">Apostichopus japonicus</Emphasis> (Selenka) induced by corn kernels meal and soybean meal in diets

The present study was conducted to determine the change of digestive physiology in sea cucumber Apostichopus japonicus(Selenka) induced by corn kernels meal and soybean meal in diets. Four experimental diets were tested, in which Sargassum thunbergii was proportionally replaced by the mixture of corn kernels meal and soybean meal. The growth performance, body composition and intestinal digestive enzyme activities in A. japonicus fed these 4 diets were examined. Results showed that the sea cucumber exhibited the maximum growth rate when 20% of S. thunbergii in the diet was replaced by corn kernels meal and soybean meal, while 40% of S. thunbergii in the diet can be replaced by the mixture of corn kernels meal and soybean meal without adversely affecting growth performance of A. japonicus. The activities of intestinal trypsin and amylase in A. japonicus can be significantly altered by corn kernels meal and soybean meal in diets. Trypsin activity in the intestine of A. japonicus significantly increased in the treatment groups compared to the control, suggesting that the supplement of corn kernels meal and soybean meal in the diets might increase the intestinal trypsin activity of A. japonicus. However, amylase activity in the intestine of A. japonicus remarkably decreased with the increasing replacement level of S. thunbergii by the mixture of corn kernels meal and soybean meal, suggesting that supplement of corn kernels meal and soybean meal in the diets might decrease the intestinal amylase activity of A. japonicus.     

Effects of a Potential Autochthonous Probiotic Bacillus subtilis 2-1 on the Growth and Intestinal Microbiota of Juvenile Sea Cucumber,Apostichopus japonicus Selenka

The effects of Bacillus subtilis 2-1 from the intestine of healthy sea cucumber on the growth, digestive enzyme activities and intestinal microbiota of juvenile sea cucumber(Apostichopus japonicus) were determined in the present study. Sea cucumber was fed with Sargassum thunbergii powder supplemented with B. subtilis 2-1 at different concentrations varying among 0(control), 10~5, 10~7, and 10~9 CFU g~(-1) for 8 weeks. Results showed that the growth performance and intestinal amylase and trypsin activities were significantly increased by dietary B. subtilis 2-1 at 10~9 CFU g~(-1)(P 0.05). However, dietary B. subtilis 2-1 had no significant influence on the lipase activity in sea cucumber(P 0.05). The polymerase chain reaction denaturing gradient gel electrophoresis and 16S rRNA gene sequencing analysis indicated that dietary B. subtilis 2-1 at 105 and 107 CFU g~(-1) inhibited most of the Proteobacteria including those in genus Vibrio. Dietary B. subtilis 2-1 at 10~9 CFU g~(-1) not only decreased the abundance and species of genus Vibrio, but also increased the intensity of genera Psychrobacter and Bacillus. A specific dosage of dietary B. subtilis 2-1 could increase the growth and modulate the intestinal microbiota of sea cucumber; thus it might be a novel probiotic for keeping the health of sea cucumber.     

Effects of Dietary Stachyose on Growth Performance,Digestive Enzyme Activities and Intestinal Morphology of Juvenile Turbot(Scophthalmus maximus L)

A 12-week feeding trial was conducted to evaluate the effects of dietary stachyose on the growth performance, digestive enzymes activities and intestinal structures of juvenile turbot(Scophthalmus maximus L). Five isonitrogenous(49.58% crude protein) and isolipidic(10.50% crude lipid) diets were formulated to contain 0(Control), 0.625%(S-0.625), 1.25%(S-1.25), 2.5%(S-2.5) and 5%(S-5) stachyose, respectively. With the increase of stachyose level, the growth performance and feed utilization of turbot, such as the specific growth rate, final mean body weight, weight gain rate and feed efficiency, increased significantly(P 0.05) and then stabilized. The feed intake of fish fed S-5 was significantly higher(P 0.05) than that of fish in other groups. The activities of trypsin, intestinal caseinolytic, stomach and intestinal amylase were significantly influenced by stachyose(P 0.05). The highest values of trypsin and intestinal caseinolytic activities were observed in group S-1.25, while the highest activity of stomach amylase and the lowest activity of intestine amylase were observed in group S-5. No lesion or damage was found on the distal intestine structures of fish from all treatments, while the height of simple folds in the distal intestine was significantly increased(P 0.05) when 1.25% or 2.5% stachyose was added in the diets. These results indicated that moderate level of stachyose(1.25%) improves the growth performance, feed utilization, digestive enzyme activities and the distal intestine structures of juvenile turbot.     

Effects of Pseudoalteromonas sp. BC228 on digestive enzyme activity and immune response of juvenile sea cucumber (Apostichopus japonicus)

A marine bacterium, Pseudoalteromonas sp. BC228 was supplemented to feed in a feeding experiment aiming to determine its ability of enhancing the digestive enzyme activity and immune response of juvenile Apostichopus japonicus. Sea cucumber individuals were fed with the diets containing 0(control), 105, 107 and 109 CFU g-1 diet of BC228 for 45 days. Results showed that intestinal trypsin and lipase activities were significantly enhanced by 107 and 109 CFU g-1 diet of BC228 in comparison with control(P 0.01). The phagocytic activity in the coelomocytes of sea cucumber fed the diet supplemented with 107 CFU g-1 diet of BC228 was significantly higher than that of those fed control diet(P 0.05). In addition, 105 and 107 CFU g-1 diet of BC228 significantly enhanced lysozyme and phenoloxidase activities in the coelomic fluid of sea cucumber, respectively, in comparison with other diets(P 0.01). Sea cucumbers, 10 each diet, were challenged with Vibrio splendidus NB13 after 45 days of feeding. It was found that the cumulative incidence and mortality of sea cucumber fed with BC228 containing diets were lower than those of animals fed control diet. Our findings evidenced that BC228 supplemented in diets improved the digestive enzyme activity of juvenile sea cucumber, stimulated its immune response and enhanced its resistance to the infection of V. splendidus.     

Characterization and identification of enzyme-producing microflora isolated from the gut of sea cucumber Apostichopus japonicus

Gut microorganisms play an important role in the digestion of their host animals. The purpose of this research was to isolate and assess the enzyme-producing microbes from the Apostichopus japonicus gut. Thirty-nine strains that can produce at least one of the three digestive enzymes(protease,amylase,and cellulase) were qualitatively screened based on their extracellular enzyme-producing abilities. The enzyme-producing strains clustered into eight groups at the genetic similarity level of 100% by analyzing the restriction patterns of 16 S rDNA amplified with Mbo I. Phylogenetic analysis revealed that 37 strains belonged to the genus Bacillus and two were members of the genus Virgibacillus. Enzyme-producing capability results indicate that the main enzyme-producing microflora in the A. japonicus gut was Bacillus,which can produce protease,amylase,and cellulase. Virgibacillus,however,can only produce protease. The high enzyme-producing capability of the isolates suggests that the gut microbiota play an important role in the sea cucumber digestive process.     

配饵中不同大豆浓缩蛋白含量对中华绒螯蟹消化酶活力的影响(英文)

研究了大豆浓缩蛋白作为饵料蛋白源对中华绒螯蟹幼蟹消化酶活力的影响,初步探讨了中华绒螯蟹对饵料蛋白源的内在适应机理。根据中华绒螯蟹的营养需求,用大豆浓缩蛋白替代鱼粉作为蛋白源配制成6种近似等蛋白等能的饵料,其中大豆浓缩蛋白在饵料中的含量分别为0、11%、22%、33%、44%和56%(分别替代鱼蛋白质量的0、18.64%、37.93%、56.90%、77.19%和100%),对照饵料全部以鱼粉作为蛋白源。用上述6种饵料喂养中华绒螯蟹50 d后,测定蟹肝胰腺各种消化酶活力。结果表明:随着饵料中大豆浓缩蛋白含量的升高,胃蛋白酶和胰蛋白酶活力均呈降低之势。当大豆浓缩蛋白含量达到44%时,与全鱼粉对照组相比,胃蛋白酶和胰蛋白酶活力显著性降低(P<0.05);同时,淀粉酶稍呈升高之势,而纤维素酶则稍呈降低的趋势;A/T比例呈显著上升的趋势,当大豆浓缩蛋白含量达44%时,与对照组有显著性差异,说明河蟹对植物蛋白有很强的适应性。     

A Study on the Meat and Bone Meal and Poultry By-product Meal as Protein Substitutes of Fish Meal in Practical Diets for Litopenaeus vannamei Juveniles

1　Introduction　Proteinisanimportantnutritionalingredientofaquaticfeed .Thehighproteinneedsoffish ,shrimpandmostotheraquaticanimalsissuppliedmainlybyfishmeal (WilliamsandBarlow ,1996 ) .Recently ,thefishmeal,asamainproteinsourceofaquaticfeedisshort suppliedintheinternationalmarketanditspriceisbecominghigherandhigher .Therefore ,itisnecessarytofindsubstitutesoffishmealasaproteinsourceofaquaticfeed .　Someotheranimalby productmealssuchasmeatandbonemeal (MBM )andpoultryby productmeal(PBM )ha…     

Colonization and Probiotic Effect of Metschnikowia sp. C14 in the Intestine of Juvenile Sea Cucumber,Apostichopus japonicus

Viable cell count was used to determine whether Metschnikowia sp.C14 can colonize the intestine of juvenile sea cucumber Apostichopus japonicus.Sea cucumber individuals were divided into two groups,which were fed the control diet for 38 days or the C14-supplemented diet at 105 cells g−1 diet for 28 days,then the control diet from day 29 to day 38.The number of C14 cells in the intestine of sea cucumber fed the C14-supplemented diet significantly increased from day 7 to day 28,and decreased from day 29 to day 38.Sea cucumber fed with the diet containing C14 showed a significant increase in trypsin activity and lipase activity from day 21 to day 33 compared with the control.Feeding C14 significantly improved the phagocytic activity and respiratory burst in coelomocytes from day 21 to day 35 and from day 14 to day 38,respectively.In addition,there was an obvious enhancement in lysozyme activity(from day 21 to day 38 or day 33),phenoloxidase activity(from day 21 to day 28)and total nitric oxide synthase activity(from day 14 to day 38)in coelomic fluid supernatant and/or coelomocyte cell lysate supernatant compared with the control.There were significant positive correlations between the number of C14 cells colonizing the intestine and trypsin activity of the intestine,lysozyme activity of the coelomic fluid supernatant and coelomocyte lysate supernatant from sea cucumber.These data suggested that the number of C14 cells should be maintained at 105 cfu(colony-forming units)g−1 intestine material for the maximum benefit.     

Effect of water temperature on digestive enzyme activity and gut mass in sea cucumber Apostichopus japonicus （Selenka）, with special reference to aestivation

The effect of water temperature on gut mass and digestive enzyme activity in sea cucumber Apostichopus japonicus, including relative gut mass (RGM), amylase, lipase, pepsin and trypsin activities were studied at temperatures of 7, 14, 21, and 28°C over a period of 40 days. Results show that RGM significantly decreased after 40 days at 21°C and markedly decreased over the whole experiment period at 28°C; however, no significant effect of duration was observed at 7 or 14°C. At 14°C, trypsin activity significantly decreased over 10 and 20 days, then increased; amylase and trypsin activity significantly decreased after 40 days at 28°C. However, no significant effect of duration was found on amylase, pepsin or trypsin activities in the other temperature treatment groups. At 28°C, lipase activity peaked in 20 days and then markedly decreased to a minimum at the end of the experiment. On the other hand, pepsin activity at 28°C continuously increased over the whole experimental period. Principle component analysis showed that sea cucumbers on day 40 in the 21°C group and in the previous 20 days in the 28°C group were in the prophase of aestivation. At 28°C, sea cucumbers aestivated at 30–40 days after the start of the experiment. It is concluded that the effect of temperature on the digestion of A. japonicus is comparatively weak within a specific range of water temperatures and aestivation behavior is accompanied by significant changes in RGM and digestive enzyme activities.     

高淀粉水平下精氨酸对松浦镜鲤肠道形态与功能的影响

【目的】探讨高淀粉饲料中添加精氨酸对松浦镜鲤(CyprinuscarpioL.)肠道消化酶活性及肠道形态的影响。【方法】选用初始体质量(6.84±0.02)g的松浦镜鲤360尾,随机分为5组,每组4个重复,每个重复18尾鱼。实验饲料分为5组,分别在45%水平的高淀粉饲料中添加质量分数0%、0.6%、1.2%、1.8%、2.4%的精氨酸,实验周期为8周,进行肠道消化酶和形态的测定。【结果】前、中、后肠的淀粉酶活性,各组之间没有显著差异(P> 0.05);添加2.4%精氨酸组的前肠脂肪酶活性显著高于对照组(P <0.05),中肠和后肠的脂肪酶活性各组间没有显著差异(P>0.05);前、中、后肠蛋白酶活性随精氨酸添加量的增加而增加,添加1.8%和2.4%精氨酸组的前肠和中肠蛋白酶活性显著高于对照组(P<0.05),添加2.4%精氨酸组后肠的蛋白酶活性显著高于对照组(P<0.05)。高淀粉饲料中添加Arg显著影响了肠道皱襞高度,但对肠绒毛宽度和肌层厚度没有显著影响。2.4%精氨酸组前肠皱襞高度显著高于其他各组(P <0.05),1.8%精氨酸组中肠和后肠皱襞高度显著高于对照组(P <0.05)。1.2%、1.8%和2.4%组肠体指数显著高于对照组(P <0.05),2.4%精氨酸组肠长指数显著高于对照组(P <0.05)。各组前、中、后肠肠绒毛密度没有显著差异,且排列较整齐。【结论】高淀粉饲料中添加1.8%~2.4%精氨酸可以增加松浦镜鲤肠道消化酶活性,同时改善了松浦镜鲤的肠道形态结构。     

3种蛋白源替代鱼粉对褐点石斑鱼幼鱼血液指标的影响

以全鱼粉饲料为对照(D1组),用豆粕替代10%、20%的鱼粉(D2、D3组),玉米蛋白粉替代10%的鱼粉(D4组),啤酒酵母替代10%的鱼粉(D5组),配制5组等氮等能饲料,研究不同蛋白源替代饲料中的鱼粉对褐点石斑鱼(Epinephelus fuscoguttatus)幼鱼血液生理生化指标的影响.结果发现:投喂56 d后,D5组终末体质量显著小于D1组和D2组(p<0.05),其他各组间差异不显著(p>0.05);D1组和D2组实验鱼体质量与D5组差异显著(p<0.05).D3组血红蛋白浓度、血栓细胞密度和平均血栓细胞体积显著低于D1组(p<0.05), D4组实验鱼嗜中性粒细胞密度和巨大不成熟细胞比例显著高于D1组(p<0.05).D3组实验鱼总蛋白含量显著低于D1、D4组(p<0.05),D3组球蛋白含量显著低于D1组(p<0.05),D3组白球蛋白比显著高于其他各组(p<0.05);D3组的血糖含量显著低于D1组(p<0.05),D2、D3、D5组的甘油三酯含量显著低于D1、D4组(p<0.05);D5组肌酐含量显著低于D1组(p<0.05).以上结果表明,酵母蛋白替代饲料中10%的鱼粉对实验鱼的生长和生理状态均产生不良影响,不适于作为褐点石斑鱼幼鱼饲料的鱼粉替代物;玉米蛋白粉和豆粕蛋白可以作为褐点石斑鱼幼鱼饲料中鱼粉的替代物,但替代比例玉米蛋白粉不宜超过10%,而豆粕蛋白的替代比例应小于20%.     

Comparison of intestinal microbiota and activities of digestive and immune-related enzymes of sea cucumber A postichopus japonicus in two habitats

Sea cucumber A postichopus japonicus stock enhancement by releasing hatchery-produced seeds is a management tool used to recover its population under natural environmental conditions. To assess the suitability of releasing sites, we examined the microbiota of the gut contents of A. japonicus from two populations(one in sandy-muddy seagrass beds and one in rocky intertidal reefs) and the microbiota in their surrounding sediments. The activities of digestive and immune-related enzymes in the A. japonicus were also examined. The results indicated that higher bacterial richness and Shannon diversity index were observed in all the seagrass-bed samples. There were significant differences in intestinal and sediment microorganisms between the two habitats, with a 2.87 times higher abundance of Firmicutes in the seagrass bed sediments than that in the reefs. Meanwhile, Bacteroidetes and Actinobacteria were significantly higher abundant in the gut content of A. japonicus from seagrass bed than those from the reefs. In addition, the seagrass-bed samples exhibited a relatively higher abundance of potential probiotics. Principal coordinates analysis and heatmap showed the bacterial communities were classifi ed into two groups corresponding to the two habitat types. Moreover, compared to A. japonicus obtained from rocky intertidal habitat, those obtained from the seagrass bed showed higher lysozyme, superoxide dismutase and protease activities. Our results suggest that bacterial communities present in seagrass beds might enhance the digestive function and immunity of A. japonicus. Therefore, compared with the rocky intertidal reef, seagrass bed seems to be more beneficial for the survival of A. japonicus.     

Effect of dietary genistein on growth performance,digestive enzyme activity,and body composition of Nile tilapia <Emphasis Type="Italic">Oreochromis niloticus</Emphasis>

An 8-week feeding experiment was performed to evaluate the effect of dietary genistein on growth performance, body composition, and digestive enzymes activity of juvenile Nile tilapia (Oreochromis niloticus). Four isonitrogenous and isoenergetic diets were formulated containing four graded supplements of genistein: 0, 30, 300, and 3 000 μg/g. Each diet was randomly assigned in triplicate to tanks stocked with 15 juvenile tilapia (10.47±1.24 g). The results show that 30 and 300 μg/g dietary genistein had no significant effect on growth performance of Nile tilapia, but the higher level of genistein (3 000 μg/g) significantly depressed the final body weight and specific growth rate. There was no significant difference in survival rate, feed intake, feed efficiency ratio or whole body composition among all dietary treatments. An assay of digestive enzymes showed that the diet containing 3 000 μg/ggenistein decreased stomach and hepatopancreas protease activity, and amylase activity in the liver and intestine, while a dietary level of 300 μg/g genistein depressed stomach protease and intestine amylase activities. However, no significant difference in stomach amylase activity was found among dietary treatments. Overall, the results of the present study indicate that a high level of dietary genistein (3 000 μg/g, or above) would significantly reduce the growth of Nile tilapia, partly because of its inhibitory effect on the activity of major digestive enzymes. Accordingly, the detrimental effects of genistein, as found in soybean products, should not be ignored when applied as an alternative ingredient source in aquaculture.     

不同糖源对方斑东风螺生长、饲料利用和消化酶活性的影响

以鱼粉、酪蛋白和明胶为蛋白源,分别以20%添加水平的葡萄糖、糊精、蔗糖、玉米淀粉、小麦淀粉和马铃薯淀粉为糖源,配制成6种不同糖源的等氮等能饲料,研究不同糖源对方斑东风螺幼螺生长性能、饲料利用、消化酶活性、糖原含量、蛋白质含量及肉壳比的影响。结果表明:方斑东风螺幼螺的增重率、特定生长率、饲料系数、蛋白质效率,消化酶活性、糖原含量、蛋白质含量及肉壳比均受到糖源种类的显著影响(P<0.05)。增重率、特定生长率从高至低依次为小麦淀粉组、玉米淀粉组、马铃薯淀粉组、糊精组、葡萄糖组、蔗糖组;饲料系数及蛋白质效率均以小麦淀粉组表现最好,与马铃薯淀粉组和玉米淀粉组无显著性差异,显著优于糊精组、葡萄糖组及蔗糖组。消化酶活性的分析结果表明,淀粉酶活性最高的是蔗糖组和小麦淀粉组,糊精组次之,葡萄糖组和马铃薯淀粉组的淀粉酶活性最低;各处理组脂肪酶活性存在显著差异,从高至低分依次为马铃薯淀粉组>小麦淀粉组>糊精组>玉米淀粉组>蔗糖组、葡萄糖组;蛋白酶活性以小麦淀粉组最高,其次为蔗糖组,其他糖源组并无显著差异;而内脏团糖原和肌糖原含量,除了葡萄糖组外,其他各组差异不显著(P>0.05);蛋白质含量以葡萄糖组最高,小麦淀粉组最低,而肉壳比则刚好相反,以小麦淀粉组和玉米淀粉组最高,葡萄糖组最低。以生长、饲料利用率和消化酶活性为评价指标,方斑东风螺饲料中采用小麦淀粉作为糖源效果最优。     

Effects of a Potential Autochthonous Probiotic <Emphasis Type="Italic">Bacillus subtilis</Emphasis> 2-1 on the Growth and Intestinal Microbiota of Juvenile Sea Cucumber, <Emphasis Type="Italic">Apostichopus japonicus</Emphasis> Selenka

The effects of Bacillus subtilis 2-1 from the intestine of healthy sea cucumber on the growth, digestive enzyme activities and intestinal microbiota of juvenile sea cucumber (Apostichopus japonicus) were determined in the present study. Sea cucumber was fed with Sargassum thunbergii powder supplemented with B. subtilis 2-1 at different concentrations varying among 0 (control), 10⁵, 10⁷, and 10⁹ CFU g^?1 for 8 weeks. Results showed that the growth performance and intestinal amylase and trypsin activities were significantly increased by dietary B. subtilis 2-1 at 10⁹ CFU g^?1 (P < 0.05). However, dietary B. subtilis 2-1 had no significant influence on the lipase activity in sea cucumber (P > 0.05). The polymerase chain reaction denaturing gradient gel electrophoresis and 16S rRNA gene sequencing analysis indicated that dietary B. subtilis 2-1 at 10⁵ and 10⁷ CFU g^?1 inhibited most of the Proteobacteria including those in genus Vibrio. Dietary B. subtilis 2-1 at 10⁹ CFU g^?1 not only decreased the abundance and species of genus Vibrio, but also increased the intensity of genera Psychrobacter and Bacillus. A specific dosage of dietary B. subtilis 2-1 could increase the growth and modulate the intestinal microbiota of sea cucumber; thus it might be a novel probiotic for keeping the health of sea cucumber.     

An Evaluation on the Ratio of Plant to Animal Protein in the Diet of Juvenile Sea Cucumber(Apostichopus japonicus): Growth,Nutrient Digestibility and Nonspecific Immunity

This study was conducted to evaluate the effects of plant/animal(P/A) protein ratios(viz.1:4, 1:3, 1:2, 1:1,2:1, 3:1, 4:1) on growth performance, body composition, apparent digestibility of diets, and nonspecific immunity of juvenile sea cucumber(Apostichopus japonicus). Sea cucumbers were divided into 21 plastic tanks, and each tank was stocked with 15 individuals(initial weight: about 23.73 g). Each feed was allocated to three replicates of sea cucumbers. The feeding experiment lasted for 50 days. Results indicated that weight gain rate(WGR) and body wall weight(BWW) significantly increased as dietary ratio of P/A increased from 1:4 to 3:1, and then decreased significantly with further increase of this ratio(P 0.05). The body wall coefficient(BWC) showed a similar tendency to WGR and BWW, but no significance was detected among dietary treatments(P 0.05). The apparent digestibility of dry matter, protein and lipid increased with ratio of P/A increasing from 1:4 to 2:1(P 0.05), and then decreased with further increase of this ratio. Correspondingly, activities of trypsin and amylase were significantly increased as P/A increased from 1:4 to 2:1(P 0.05). The activities of SOD and CAT showed a similar trend with WGR, with the highest value observed in the ratio of 1:2 and 1:1, respectively. Results above showed that moderate or relatively higher ratio of P/A protein(1:1-3:1) significantly increased the growth performance, apparent digestibility, and nonspecific immunity of sea cucumber. This will contribute to improving the feed formulation for juvenile cucumbers.     

High-throughput sequencing of 16S r RNA amplicons characterizes gut microbiota shift of juvenile sea cucumber Apostichopus japonicus feeding with three antibiotics

Sea cucumber Apostichopus.japonicus is an important marine economic species in Asian countries due to its profound nutritional and medicinal value.So far,with the rapid development of intensified artificial aquaculture of sea cucumbers,the use of antibiotics is still an inexpensive and dispensable way to treat pathogenic infections,especially during the nursery phase.However,there is little information on the effects of antibiotics on the intestinal microbiota of sea cucumber.Therefore an Illumina based sequencing method was used to examine the intestinal bacterial composition of juvenile A.japonicas following diets with three typical antibiotics(tetracycline,erythromycin.,and norfloxacin)under 15,30,and 45 d.The findings reveal that different antibiotics have distinct effects on the growth performance of juvenile sea cucumbers.However,the richness and diversity of microbiota were barely affected by antibiotics but the community composition alterations indicated that the three antibiotics exhibited their respective patterns of reshaping the intestinal bacteria of juvenile sea cucumbers.In common,the abundance of some sensitive genera with helpful functions,such as Thalassotalea,Shewanella,Sulfitobacter,and Halomonas decreased significantly with exposure to antibiotics and the abundance of multiple potential pathogenic-and suspected antibiotic-resistant microorganisms like Arcobacter,Leucothrix,and Clostridium_sensu_stricto_1 was found increased significantly in the antibiotic groups.These results suggest that low doses of antibiotics could affect the composition of the intestinal microbiota of sea cucumbers and might increase the risk of infection of the hosts.This study could help us to explore how antibacterial compounds modify the gut microbiota of sea cucumbers and provide theoretical guidance in hatchery management by scientific antibiotic use in sea cucumber mariculture.     

Effects of Hanseniaspora opuntiae C21 on the growth and digestive enzyme activity of juvenile sea cucumber Apostichopus japonicas

The effects of a diet containing Hanseniaspora opuntiae C21 on growth and digestive enzyme activity were estimated in juvenile Apostichopus japonicus. Groups of sea cucumbers were fed diets containing H. opuntiae C21 at 0(control), 10 4, 10 5, and 10 6 CFU(colony-forming units)/g feed. Results showed that after 45 d the specific growth rate(SGR) of sea cucumbers fed a C21-supplemented diet at 10 4 CFU/g feed was significantly higher than that of the control( P 0.05). Intestinal trypsin and lipase activities were significantly enhanced by C21 administration at 10 4 and 10 5 CFU/g feed compared with the control( P 0.05). After feeding for 23–42 d, C21 was demonstrated by denaturing gradient gel electrophoresis to be present in the intestine of sea cucumbers. In addition, after feeding the C21-supplemented diets for 15 d, the sea cucumbers were switched to an unsupplemented diet and C21 was confirmed to be capable of colonizing the intestine for at least 31 d after cessation of feeding. In conclusion, C21 was shown to successfully colonize the intestine of juvenile A. japonicus via dietary supplementation, and improve growth and digestive enzyme activity.     

Effects of Replacing Fishmeal with Animal By-products Meal Supplementation in Diets on the Growth and Nutrient Utilization of Mangrove Red Snapper

A feeding trial was conducted for 75 d to evaluate the nutritive value of a mixture of animal by-products(MAB) as a possible protein source in diets for juvenile mangrove red snapper,Lutjanus argentimaculatus(mean initial body weight,30 g). Fish were fed one of five isonitrogenous diets(40% crude protein) replacing 0,25%(MAB25),50%(MAB50),75%(MAB75) and 100%(MAB100) of fish meal protein with similar percentages of MAB. The MAB consisted of 25% cow liver meal,20% leather meal,20% meat and bone meal,15% blood meal,10% APC(poultry feather meal),8% poultry manure dried,1.5% choline and 0.5% chromic oxide. After 75 d of feeding,fish fed with diets MAB50,MAB75 and MAB100 exhibited significantly lower growth per-formance than that of fish fed with control and MAB25 diets. The optimum level of MAB was estimated to be 23%. Replacement of fish meal by MAB23% showed the following performance:maximum weight gain,510%;SGR,2.39% and FCE,2.83%. The MAB substitution up to 75% of fish meal protein in diets did not show differences in apparent protein digestibility(83.6% for MAB25,79.2% for MAB50,78.7% for MAB75) compared with control(83.4%),whereas in MAB100 group digestibility(65.3%) was sig-nificantly lower than in other groups. The apparent phosphorus absorption of test diet groups was significantly higher(37.1% for MAB25,28.5% for MAB50,55.6% for MAB75 and 54.5% for MAB100) than that of control(11.2%). The levels of protein and ash in the whole body,carcass and viscera increased as MAB substitution in diets increased,whereas lipids and moisture remained con-sistent among all treatment groups. These results showed that approximately 23% of fish meal protein could be replaced by a mixture of animal by-products for juvenile snapper growing from 30 g to 167 g in 75 d without compromising growth performance and feed efficiency.