Feeding and gut evacuation of cultured juvenile spiny lobsters, Jasus edwardsii

Low feed consumption has been suggested as a major impediment for the development of effective formulated diets for spiny lobsters. To seek an explanation for the low feed consumption, this study compared the feed consumption, appetite revival, foregut evacuation and fecal production of different sizes of spiny lobster Jasus edwardsii juveniles fed a fresh natural diet (i.e. mussel flesh) and a dry formulated diet. In addition, the effect of feeding frequency was determined by feeding juvenile lobsters the same ration of formulated diet at different time intervals. i.e., same ration delivered 3 week^− 1, 1 day^− 1, 2 day^− 1, 5 day^− 1 and 5 night^− 1. Lobster (10–15 g) growth and feed consumption (1.15% BW day^− 1) was maximized when receiving a single ration daily of the formulated diet. A slow appetite revival (AR > 18 h) on the formulated diet was consistent with the negative effect of increasing feeding frequency on growth and consumption. In addition, there appeared to be no major advantage in dry matter intake by providing the nutrient dense dry formulated diet to Jasus edwardsii. Lobsters fed fresh mussel flesh (79.8% moisture) consumed similar levels of dry matter as those lobsters fed the dry formulated feed (7.3% moisture). This appears to be due to high moisture gain and expansion of the dry feed in the lobster foregut. Foregut evacuation lasted 10 h for the two diets but a delay in initial foregut evacuation and processing of the formulated diet was evident, and may have negatively affected feed consumption, appetite revival and dry matter digestibility (61.2%) of the dry formulated diet compared to the mussel flesh diet (89.2%). Appetite revival on mussel flesh was almost complete by 12 h after a satiation ration and was governed primarily by the rate of foregut evacuation. Differences in the timing of foregut evacuation and fecal production between the two diets suggested that a greater proportion of the formulated diet entered the midgut directly.The results indicate that J. edwardsii cannot achieve high levels of feed consumption on formulated diets because gut throughput is reduced due to a small foregut capacity, expansion of the feed post-ingestion, lengthy foregut filling time (1–2 h) and clearance time (10 h), combined with slow gut throughput time (34–42 h) and appetite revival (> 18 h). A slow appetite revival and difficulties in processing and digestion of formulated diets appear as major issues to be resolved to improve the performance of formulated diets required for the commercial aquaculture of J. edwardsii and possibly other spiny lobsters.     

Effects of dietary carbohydrate on growth of juvenile New Zealand rock lobsters, Jasus edwardsii

The commercial aquaculture of spiny lobsters is impeded by the development of effective practical diets, which is partly due to a lack of knowledge of the digestive capabilities and nutritional needs of these species. Carbohydrates have the potential to provide a low cost energy source in practical diets for spiny lobsters. This research investigated the effect of algal carbohydrates, on the growth of juvenile rock lobsters. Juvenile lobsters, Jasus edwardsii, (10-12 mm carapace length) were provided with one of five diets; blue mussel, squid (Nototodarus gouldii), or a mussel diet partially substituted with algal carbohydrates, either agar, carrageenan or alginate over 80 days in culture. In all treatments, diet consumption and lobster growth were maintained or increased over time. Growth was highest for the mussel diet followed by the agar diet. Similar lobster growth occurred on the carrageenan and alginate diets, with the least on the squid diet. After 80 d there were significant differences in the percent lipid and glycogen stored in the mid-gut gland with highest levels of glycogen in lobsters fed the mussel only diet. Percent protein in the tail muscle was greatest for mussel fed lobsters. The mid-gut index (mid-gut weight/whole wet weight) was highest for the mussel only diet and this was similar to control lobsters at the start of the experiment. The results indicate that glycogen from mussels and agar could be used as carbohydrate source in the future development of a practical diet for spiny lobsters.     

An evaluation of the nutritional value of alternative lipid sources to juvenile southern rock lobster, Jasus edwardsii

Experimental lobster feeds are currently based on fish meal and fish oil formulations, and although survival and growth similar to that of lobsters fed fresh blue mussels has been achieved, varying the protein level in previous experimental feeds has not increased growth beyond that of lobsters fed natural food. This experiment assessed the growth performance of lobsters fed pelleted feeds containing constant amounts of protein, lipid and energy where the lipid was provided by a range of oil-rich ingredients (fish oil, FO; fish oil with added soybean lecithin, FOL; canola oil, CO; tuna oil, TO; mussel meal, MM; and squid meal, SQM). Feed performance was assessed by lobster growth rate, survival, final biochemical composition, nutrient retention and nutrient efficiency. Twenty tanks containing 15 post-larval lobsters each (1.5 ± 0.04 g) were randomly allocated one of six test feeds in triplicate, and the two remaining tanks were fed freshly opened blue mussels (FRM) as a reference feed. Lobsters were fed daily to excess for 10 weeks. Final individual weights of whole body and digestive gland were measured, and tissue chemical composition analysed. There were no significant differences in survival (88.4 ± 3.3%), or specific growth rate (1.3 ± 0.1%.day^− 1) among the formulated feed fed lobsters, which were significantly lower than the survival (100 ± 0.0%) and SGR (2.2 ± 0.1%.day^− 1) of FRM fed lobsters. The SQM fed lobsters had a significantly lower lipid efficiency ratio and lipid productivity value than lobsters fed TO, FOL and MM feeds. The digestive gland lipid content (g.100 g wet tissue^− 1) of lobsters fed the feeds TO (3.7 ± 0.4), FO (3.5 ± 0.3) and SQM (2.2 ± 0.2) were significantly lower than lobsters fed feeds MM (9.9 ± 1.1), FOL (9.0 ± 2.3) and FRM fed lobsters contained most digestive gland lipid (12.3 ± 1.5).     

The effect of carbohydrate source, inclusion level of gelatinised starch, feed binder and fishmeal particle size on the apparent digestibility of formulated diets for spiny lobster juveniles, Jasus edwardsii

The development of cost-effective and digestible formulated diets is essential for the commercialisation of spiny lobster aquaculture. Large juvenile spiny lobsters, Jasus edwardsii (115 g), were used to measure the apparent digestibility of formulated diets with six different carbohydrate sources, three levels of gelatinised starch, three types of binder, and two ranges of particle size of fishmeal. Carbohydrate source, inclusion level and binder type all had a significant effect on the dry matter digestibility (ranging 61–79%) of formulated diets for J. edwardsii. The digestibility of the carbohydrates included at 35% by dry weight were: dextrin (99%), carboxymethyl cellulose (CMC; ~ 94%), native wheat starch (91%), gelatinised maize starch (84%), native potato (60%) and maize (59%) starches. Gelatinised maize starch inclusion level (ranging from 15% to 55% by dry weight) was negatively correlated with starch digestibility (ranging from 92% to 79% respectively). Dry matter digestibility of the diets was improved by using gelatine (73%) instead of alginate (68%) and agar (61%) as a binder. Nitrogen digestibility (ranging 82–89%) did not differ significantly among diets. Reducing the particle size distribution of the fishmeal from < 500 µm to < 106 µm did not improve digestibility. The results indicate that using digestible carbohydrate sources (dextrin, CMC, and native wheat starch) for energy, reducing the inclusion level of gelatinised starch, and using CMC or gelatine as binders improve the apparent digestibility of formulated diets. Furthermore, the results also indicate that the use of more soluble and pre-hydrolysed protein sources in diets for J. edwardsii may greatly improve digestibility which is critical in these spiny lobsters where overall food intake is limited.     

Dietary carbohydrate/lipid ratios and nutritional condition in juvenile southern rock lobster, Jasus edwardsii

The availability of formulated diets is considered economically imperative if rock lobster aquaculture, based on the collection and ongrowing of puerulus, is to progress. Central to the development of diets is an understanding of the nutritional requirements of the species. This study determined the effect of different dietary carbohydrate/lipid ratios (17:1, 5:1, 2:1, 0.8:1) on the growth and nutritional condition of juvenile southern rock lobsters, Jasus edwardsii, by measuring standard growth parameters, proximate composition of the whole body and digestive gland, and from a histological investigation of the digestive gland. Four replicate groups of eight lobsters (initial weight 5.08±0.98 g (mean±S.D.)) per diet treatment were held in 50 l tanks, in a recirculating system at 18 °C for 84 days. Maximum growth and the highest levels of lipid and dry matter in digestive glands and whole bodies was found in lobsters fed a diet containing 27% carbohydrate and 13.5% lipid (2:1 ratio) suggesting that of the four experimental diets, this diet provided the best balance of lipid and carbohydrate. Digestive gland histology supported this conclusion and lobsters fed low carbohydrate, high lipid diets were in the best nutritional condition, with high lipid accumulation, and structurally sound epithelial cells. Digestive gland epithelial cells of lobsters fed the high carbohydrate, low lipid diets were compressed, of inconsistent shape and size, with low lipid accumulation. Histology is therefore seen as a feasible method, in addition to growth and proximate composition data, to further examine the effect of diets in nutritional studies of crustaceans.     

Morphological and biochemical characteristics of phyllosoma after photothermal manipulation of reproduction in broodstock of the spiny lobster, Jasus edwardsii

The consequences of photothermal manipulation of reproduction in Jasus edwardsii broodstock on the morphology of newly hatched larvae and their biochemical characteristics were examined. The treatment of compressed temperature and photoperiod delayed the time of moult, mating and egg extrusion, but reduced the period until larval hatch, and reduced the hatching duration in individual females compared to the ambient treatment of simulated natural photoperiod and water temperature. Thus, the availability of phyllosoma for hatchery rearing was extended. However, the broodstock in the compressed treatment produced smaller phyllosoma and more larvae failed to develop beyond the naupliosoma stage than animals from the ambient cycle. Phyllosoma from the compressed treatment contained a higher proportion of polar and triacylglycerol lipid classes, lower wax esters, elevated levels of the essential fatty acid docosahexaenoic acid, a higher ratio of n-3/n-6 fatty acids, and lower levels of ascorbic acid. The changes in larvae from the compressed treatment may adversely affect their viability, and are probably due to the higher water temperatures experienced during late embryonic development.     

不同碳水化合物和蛋白质水平膨化饲料对大规格草鱼生长、肠道消化酶及血清指标的影响

为确定吉富罗非鱼(GIFT Oreochromis niloticus)成鱼饲料中适宜的碳水化合物与脂肪比例(C/L),实验设计了6组等氮等能的半纯化饲料,饲料C/L比例分别为1.53、2.36、3.55、5.58、9.85、21.82。投喂初始质量为(218.33±11.03) g的吉富罗非鱼成鱼56 d。结果显示,增重率和特定生长率在C/L比例为3.55时最高,显著高于C/L比例1.53、9.85和21.82组 (P<0.05);饲料效率和蛋白质效率在C/L比例介于2.36~5.58时无显著差异,显著高于1.53和21.82组(P<0.05)。随着饲料C/L比例的升高,肝体比和脏体比呈显著下降趋势(P<0.05),成活率各组无显著差异(P>0.05)。全鱼和肝脏的粗脂肪含量随饲料C/L比例的增加显著降低(P<0.05)。血清甘油三酯(TG)和高密度脂蛋白胆固醇(HDL-C)含量随C/L比例升高而下降,低密度脂蛋白胆固醇(LDL-C)和血糖(GLU)含量则呈显著上升趋势(P<0.05)。分别利用二次多项式回归分析增重率、蛋白质效率和饲料效率与碳水化合物水平及脂肪水平的相关性,得到饲料中适宜的C/L比例分别是4.19、4.15和4.11。研究表明吉富罗非鱼成鱼饲料中适宜的C/L比例为4.11~4.19。

     

Effect of dietary carbohydrate level on growth performance of juvenile spotted Babylon (Babylonia areolata Link 1807)

A growth trial was conducted to determine the effects of dietary carbohydrate level on growth performance, feed utilization and metabolism of juvenile spotted babylon. Six isonitrogenous and isoenergetic experimental diets (48% crude protein and 15 MJ kg^− 1 diet) using wheat starch as the carbohydrate source, were formulated to contain six carbohydrate levels. Triplicate groups of 45 animals (initial average weight, 168.39 ± 0.69 mg) were stocked in 120-l tanks and fed to apparent satiation twice daily for 10 weeks. Growth performance and feed utilization were significantly affected by dietary carbohydrate level. Maximum weight gain and specific growth rate occurred at 20% dietary starch inclusion, survival and soft body to shell ratios were not significantly different among diets. There were significant differences in protein, lipid, moisture and glycogen content in soft body. Glycogen content in soft body was positively correlated with dietary starch level. The activities of glucose-6-phosphate dehydrogenase and fructose-1,6-bisphosphatase were significantly affected by dietary starch level, with both peaking in the 20% treatment; however, there were no significant differences in 6-phosphofructokinase activity in any treatment. Quadratic regression analysis of weight gain against dietary starch level indicated that the optimal dietary carbohydrate level for maximum weight gain of juvenile spotted babylon is 27.1% of dry diet.     

Use of formulated diets as replacements for Artemia in the rearing of juvenile American lobsters (Homarus americanus)

American lobsters, Homarus americanus, have been successfully reared in hatchery operations for over a century, yet formulated diets have never been commercially produced. In recent years, commercial Artemia replacement (CAR) diets have been developed and marketed for use in aquaculture production of marine shrimp. Three separate experiments assessed the utility of rearing American lobsters on these shrimp CAR diets. First, survival and growth of stage IV American lobsters fed one of three CAR diets (Artemac 5, CAR1; Economac 4, CAR2; and Progression 3, CAR3) were compared to those of animals fed frozen adult n-3 fatty acid enriched Artemia. Survival to 3 months was highest for animals fed CAR3 (85%), while animals fed Artemia had the greatest weight gain (> 6 % day^− 1). A cost / benefit ratio analysis showed that CAR2 was the most cost efficient for juvenile production because of its low overall purchase cost. Second, stage IV lobsters were fed either CAR2 or frozen adult n-3 fatty acid enriched Artemia exclusively, or in combination (2 : 5, and 5 : 2). Again, CAR2 was a cost effective feed to use, even as a partial replacement for Artemia. Survival was higher in diets that included CAR2, and feeding it two days per week compensated for low quality Artemia. Finally, 1.5 year old lobsters fed a gelatin-bound mix of 80% CAR2 and 20% frozen Artemia for five months survived and grew equally well compared to lobsters fed gelatin-bound frozen adult Artemia, and better than a custom formulated maintenance diet. The benefits of incorporating formulated feeds into American lobster rearing programs to increase the effectiveness of enhancement programs is discussed.     

团头鲂NK-lysin基因鉴定和表达分析

为研究抗菌肽NK-LYSIN在团头鲂免疫系统中的可能功能,本实验从团头鲂转录组中钓取到2个NK-lysin基因(nkla和nklb),通过PCR扩增并测序验证其ORF序列。通过荧光定量PCR检测其在健康组织和嗜水气单胞菌感染后免疫组织中的表达,并构建其原核表达体系。结果显示,团头鲂nkla和nklb分别编码122和136个氨基酸,NKLA和NKLB均属于鞘脂激活蛋白样蛋白家族成员,各含有6个高度保守的半胱氨酸及1个Sap B结构域。在健康团头鲂各组织中,nkla在脾脏中表达量极高,在肌肉和血液中表达量极低;而nklb则在肠中表达量较高,在头肾中表达量较低,在其他组织均有表达。nkla和nklb不同的表达模式暗示它们可能存在功能上的分化。经嗜水气单胞菌感染后,团头鲂nkla与nklb表达变化模式相似,头肾中,表达量在4 h时显著下降;肝脏中,表达量在4 h达到最高,而后回落到正常水平;在脾脏和肠中4 h时开始下降,72 h时达到峰值,暗示NK-lysin可能在团头鲂抗嗜水气单胞菌感染过程中发挥重要作用。另外,本实验对nkla和nklb进行了原核表达,为进一步研究NK-lysin的功能奠定了基础。     

不同糖源膨化饲料对大规格草鱼生长、越冬及血清部分生化指标的影响

以商业配方为基础,研究不同糖源(小麦、大麦、玉米、白高粱、木薯)膨化饲料对大规格草鱼[初始体质量(400.77±7.45) g]生长、体成分、越冬及部分生理生化指标的影响。共设置5个处理,每处理3个重复,每个重复30尾鱼,养殖实验于水库网箱(2.0 m×2.0 m×2.0 m)中进行,饲养时间为16周,养殖实验结束后,每网箱保留15尾进行越冬实验,时间为16周。结果显示,玉米组草鱼增重率(WGR)和蛋白质效率(PER)显著低于其他各组,饲料系数(FCR)显著高于其他各组,其他4组差异不显著;肥满度(CF)小麦组最高,脏体比(VSI)玉米组最高,肝体比(HSI)和肠体比(ISI)木薯组最高;小麦组血糖(GLU)含量显著高于其他各组,大麦和白高粱组总胆固醇(T-CHO)含量显著高于其他3组,木薯组甘油三酯(TG)含量显著低于其他各组。小麦、大麦和玉米组的肌肉粗脂肪含量显著高于白高粱和木薯组,木薯组的粗蛋白含量显著低于其他4组。白高粱和木薯组的肝糖原显著高于其他组,大麦和白高粱组的肌糖原显著高于其他组。越冬后,大麦组草鱼体质量下降幅度显著高于其他各组,HSI下降幅度显著小于其他各组,肝糖原含量显著升高,GLU下降幅度显著低于其他各组,肌肉粗蛋白含量下降幅度最高,其他各组越冬后体质量下降幅度差异不显著,小麦组CF下降比例最高,玉米和木薯组HSI下降幅度显著大于其他各组,玉米组的VSI下降比例最大。研究表明,在膨化工艺条件下,以生长、增重成本和越冬为评价指标,小麦、木薯和白高粱是大规格草鱼适合的糖源,木薯增重成本最低。     

大口黑鲈幼鱼饲料中白鱼粉与两种豆粕的适宜配比

用8种等氮、等能和等脂的饲料,以实验鱼的生长、体组成、饲料效率、非特异性免疫和血液学参数作指标,评定大口黑鲈幼鱼饲料中去皮豆粕和酶解豆粕分别替代白鱼粉的可行性和适宜配比。在4水平的去皮豆粕饲料(D1～D4)和酶解豆粕饲料(E1～E4)中,白鱼粉和两种豆粕的配比均分别为45∶5、40∶12、35∶18和30∶25。用上述8种饲料饲喂初始体质量(5.32±0.05)g的大口黑鲈,每饲料设3个重复,每重复35尾鱼。采用表观饱食投喂,每天饲喂2次(8:00和16:00)。结果显示,各组之间实验鱼的成活率和特定生长率无显著性差异。但当去皮豆粕和酶解豆粕在饲料中的含量分别高于5%和12%时,饲料效率和蛋白质效率显著降低。随着饲料中白鱼粉含量从45%降低至30%,饲料的蛋白质和脂肪消化率显著升高;同时,全鱼、肌肉和内脏的蛋白质和水分含量均呈显著降低,但脂肪含量却显著升高;肝体比和肝糖含量显著降低;实验鱼的血清溶菌酶活性和血清蛋白质含量显著降低,但血清补体活性无显著差异;红细胞压积和血红蛋白含量均显著降低,但红细胞数差异不显著。实验表明,大口黑鲈幼鱼饲料中白鱼粉与去皮豆粕的合适配比为45%和5%,而白鱼粉与酶解豆粕的合适配比为40%和12%;豆粕经酶处理后能去除其中的部分抗营养因子,可替代饲料中11%的白鱼粉。     

Evaluation of soybean meal in the formulated diets for juvenile Pangasianodon hypophthalmus (Sauvage, 1878)

The influence of soybean meal (SBM) on the growth and feed utilization of juvenile sutchi catfish (Pangasianodon hypophthalmus, Sauvage, 1878) was investigated. Eight isonitrogenous (300 g kg^?1 CP) and isoenergetic (18 MJ kg^?1) diets were formulated incorporating Argentine SBM to replace fish meal at 0, 150, 300, 450, 600, 750, 900 and 1000 g kg^?1 dietary protein. Each diet was fed to three replicate groups of fish with an initial weight 6.0–6.2 g for twelve weeks. Growth performance decreased, and feed utilization was worsened with the increase in SBM inclusion in the diets. Final weight and relative growth rate (RGR) of fish fed control diet (0 SBM) were significantly higher than those fed test diets (P < 0.05). However, there were no significant differences in the final weight and RGR between the fish fed on 15 SBM, 30 SBM, 45 SBM and 60 SBM diets. Specific growth rate of fish fed 0 SBM, 15 SBM, 30 SBM and 45 SBM diets was significantly higher than those fed other diets. Feed conversion ratio of fish fed 0 SBM, 15 SBM, 30 SBM, 45 SBM and 60 SBM diets was significantly lower than those fed other diets (P < 0.05). The dry matter and protein digestibility were lesser in all the diets in comparison with the control diet. Hepatosomatic index and viscerosomatic index increased with increasing SBM in diet. This present trial indicated that fish meal can be replaced by SBM in the diet of juvenile sutchi catfish only up to 45% of fish meal protein without any adverse effect on growth, feed utilization and body composition.     

三种糖源对凡纳滨对虾仔虾期饥饿和补偿生长后营养物质代谢的影响

为了解2种状态(饥饿和复投喂)下投喂3种糖源对凡纳滨对虾仔虾生长、虾体组成成分、代谢指标的影响,实验共5个处理,分别为饥饿组S0、对照组C、实验组S1、S2、S3(在基础饲料中糖源分别为：葡萄糖、蔗糖、玉米淀粉)。实验选取体质量为(1.84±0.23) g的凡纳滨对虾仔虾用方形纱制网兜独立喂养,进行为期12 d的饥饿实验后继续复投喂12 d。结果显示,饥饿后仔虾体组成成分及相关酶[脂肪酶(LPS)、磷酸果糖激酶(PFK)、已糖激酶(HK)、谷氨酰胺合成酶(GS)]差异显著;仔虾肝糖原、肌糖原均呈现出反复升降的过程,饥饿8 d后肝糖原降到最低值,肌糖原短暂回升后显著下降。复投喂4 d后S3组增重率最高,实验各组间无显著差异,均低于C组;全虾水分、全虾粗灰分、肌糖原含量无显著差异;S1、S2组虾体粗脂肪含量显著高于S3组;肝糖原、肌糖原均有回升,S1组肝糖原显著低于其他组。复投喂12 d后,S3组LPS活性、HK活性显著高于其他各实验组,GS、PFK含量实验组间无显著差异。研究表明,凡纳滨对虾仔虾饥饿过程中糖原和脂肪先于蛋白质被动用供能;复投喂出现部分补偿生长效应,玉米淀粉作为糖源饲料对凡纳滨对虾仔虾期恢复生长效果最佳。     

Effects of manganese on juvenile mulloway (Argyrosomus japonicus) cultured in water with varying salinity—Implications for inland mariculture

The effects of 5 mg/L of dissolved manganese on juvenile mulloway at salinities of 5, 15 and 45 ppt were determined by comparing their survival, growth and blood plasma and organ chemistry with those of fish grown at the same salinities without manganese addition. Survival of mulloway at 45 ppt in the presence of 5 mg/L of manganese (73 ± 13%) was significantly lower than all other treatments, which achieved 100% survival. Those fish grown in water without manganese exhibited rapid growth, which was not affected by salinity (SGR = 4.05 ± 0.29%/day). Those fish grown at 5 ppt and 45 ppt in the presence of manganese lost weight over the 2-week trial (SGR − 0.17 ± 0.42 and − 0.44 ± 0.83%/day, respectively), whilst those at 15 ppt gained some weight (SGR 1.70 ± 0.20%/day). Manganese accumulated in the gills, liver and muscle of the fish and significant differences in blood plasma chemistry were observed. Blood plasma sodium and chloride of fish exposed to manganese were significantly elevated in hyperosmotic salinity (45 ppt) and depressed at hyposmotic salinity (5 ppt) compared with unexposed fish at the same salinity; consistent with manganese causing apoptosis or necrosis to chloride cells. We did not, however, observe any gill epithelial damage under light microscopy. Blood plasma potassium was significantly elevated at all salinities in the presence of manganese and liver potassium and glycogen reduced. These findings are consistent with manganese interfering with carbohydrate metabolism.     

饲料低蛋白、高脂肪和高消化能对斑点叉尾鮰

为了探讨高脂肪条件下不同的蛋白和能量水平对斑点叉尾鮰生长及体组成的影响,试验设2个蛋白水平(22%,28%),2个脂肪水平(10.0%,14.0%),2个消化能水平(12.56 kJ/g,14.23 kJ/g),共8组,分别为P28L10E14.23,P28L14E14.23,P22L10E14.23,P22L14E14.23,P28L10E12.56,P28L14E12.56,P22L10E12.56和P22L14E12.56。试验饲料配方使用鱼粉和豆粕调节蛋白含量,混合油脂(鱼油∶玉米油=1∶1)调节脂肪含量,α-淀粉、次粉和麸皮调节消化能含量,并以微晶纤维素为填充物,每组3个重复,每个重复20尾鱼(141.5?1.0) g。饲养60 d后,进行生产性能测定,并采集组织样本,测定相关指标。结果表明,鱼体末重(FW)、增重率(WG)、特定生长率(SGR)和饵料系数(FCR)不受饲料蛋白、脂肪和消化能单一营养水平影响(P>0.05);但与饲料蛋白、脂肪和消化能三者的交互作用(P<0.01)有关。胴体蛋白、脂肪含量与饲料脂肪和消化能水平相关(P<0.05)。由此可见,饲料过高脂肪和消化能对斑点叉尾鮰没有额外的促生长作用;饲料蛋白水平达到22%时,即可满足140~300 g斑点叉尾鮰的营养需要;饲料中22%的蛋白、10%的脂肪、12.56 kJ/g的消化能即可满足斑点叉尾鮰仔鱼的生长需要,同时又能保证其正常生理机能,建议可在实际生产配方中作参考值。     

草鱼幼鱼对异亮氨酸的需要量

以初始体重（8.25±0.37） g的草鱼幼鱼为试验对象,分别采用异亮氨酸（isoleucine,Ile)水平为0.77 %、1.07 %、1.37 %、1.67 %、1.97 %和2.27 % 6组等氮(粗蛋白35.25 %)半纯化日粮对草鱼进行了72 d生长试验,研究其日粮异亮氨酸需要量。结果表明：（1）日粮Ile水平为1.67 %时,草鱼增重率、特定生长率和蛋白质效率最高,饲料系数最低;鱼体空壳率和肥满度达到最大值,内脏指数最小;草鱼体水分、体脂最低,体蛋白、灰分最高;肌肉水分最低,粗蛋白最高。而各水平之间肌肉粗脂肪无显著差异(P> 0.05);日粮Ile水平为1.67 %时,草鱼肌肉Ile含量和肌肉氨基酸总量最高。（2）随日粮Ile水平增加,肌肉RNA/DNA呈先升后降趋势,Ile 1.67 %水平组最高;而肝脏谷氨酸脱氢酶却呈先降后升趋势,Ile 1.67 %水平组最低。血氨在Ile 0.77 % ~ 1.67 %水平组之间处于稳定状态,高于1.67 %水平后呈上升趋势。血清白蛋白受日粮Ile水平的影响不显著（P> 0.05）。（3）随日粮Ile水平增加,血清甘油三酯和胆固醇均呈先降后升趋势,且在Ile 1.67%水平组,两项指标均为最低值,显著低于其他水平组（P< 0.05）。根据增重率、特定生长率、饲料系数和蛋白质效率与日粮Ile水平的二次曲线关系,确定草鱼幼鱼日粮(粗蛋白35.25 %) Ile适宜需要量范围为1.41 %～1.49 %(日粮基础)或4.0 %～4.23 %(日粮蛋白基础)。     

运输胁迫对银鲳血清皮质醇、血糖、组织中糖元及乳酸含量的影响

研究分析了运输胁迫2、4、8和12 h后银鲳血清皮质醇、血糖、组织中糖元及乳酸含量的变化。选取平均体质量为(10.05±0.23) g的银鲳幼鱼为试验对象,共设3组运输密度,分别为4、8和16 g/L。每个时间段的运输结束后,将取样后剩余的鱼转入1 m³水体的圆形玻璃钢桶中观察24 h,以统计各自的累计死亡率。研究结果显示,16 g/L密度组在运输12 h后成活率为91.25%,其余均为100%;运输胁迫导致皮质醇含量显著升高(P<0.05),运输4 h后,血清皮质醇含量均达到最高值,12 h后皮质醇含量虽较运输4 h后有所降低,但仍显著高于试验初的水平,且此时16 g/L密度组的皮质醇含量均显著高于4和8 g/L密度组(P<0.05);血糖、血清与肌肉中乳酸含量在运输胁迫后均显著升高(P<0.05);肝脏与肌肉中糖元含量在运输胁迫后均显著降低(P<0.05),但在整个运输胁迫过程中,肝脏组织中糖元含量的降低程度明显高于肌肉组织。统计分析得出,较高的运输密度会加重银鲳的应激性反应,并推测在小水体开放式运输的情况下,规格为10 g左右的银鲳幼鱼,其运输密度不宜超过16 g/L。此外,在运输胁迫下,银鲳机体的能量供给主要来自肝脏糖元的动员。     

Prediction of apparent protein digestibility of ingredients and diets by in vitro pH-stat degree of protein hydrolysis with species-specific enzymes for juvenile Pacific white shrimp Litopenaeus vannamei

Aquafeed production faces global issues related to availability of feed ingredients. Feed manufacturers require greater flexibility in order to develop nutritional and cost-effective formulations that take into account nutrient content and availability of ingredients. The search for appropriate ingredients requires detailed screening of their potential nutritional value and variability at the industrial level. In vitro digestion of feedstuffs by enzymes extracted from the target species has been correlated with apparent protein digestibility (APD) in fish and shrimp species. The present study verified the relationship between APD and in vitro degree of protein hydrolysis (DH) with Litopenaeus vannamei hepatopancreas enzymes in several different ingredients (n = 26): blood meals, casein, corn gluten meal, crab meal, distiller's dried grains with solubles, feather meal, fish meals, gelatin, krill meals, poultry by-product meal, soybean meals, squid meals and wheat gluten. The relationship between APD and DH was further verified in diets formulated with these ingredients at 30% inclusion into a reference diet. APD was determined in vivo (30.1 ± 0.5 °C, 32.2 ± 0.4‰) with juvenile L. vannamei (9 to 12 g) after placement of test ingredients into a reference diet (35 g kg^− 1 CP; 8.03 g kg^− 1 lipid; 2.01 kcal g^− 1) with chromic oxide as the inert marker. In vitro DH was assessed in ingredients and diets with standardized hepatopancreas enzymes extracted from pond-reared shrimp. The DH of ingredients was determined under different assay conditions to check for the most suitable in vitro protocol for APD prediction: different batches of enzyme extracts (HPf5 or HPf6), temperatures (25 or 30 °C) and enzyme activity (azocasein): crude protein ratios (4 U: 80 mg CP or 4 U: 40 mg CP). DH was not affected by ingredient proximate composition. APD was significantly correlated to DH in regressions considering either ingredients or diets. The relationships between APD and DH of the ingredients could be suitably adjusted to a Rational Function (y = (a + bx)/(1 + cx + dx²), n = 26. Best in vitro APD predictions were obtained at 25 °C, 4 U: 80 mg CP both for ingredients (R² = 0.86; P = 0.001) and test diets (R² = 0.96; P = 0.007). The regression model including all 26 ingredients generated higher prediction residuals (i.e., predicted APD − determined APD) for corn gluten meal, feather meal, poultry by-product meal and krill flour. The remaining test ingredients presented mean prediction residuals of 3.5 points. A model including only ingredients with APD > 80% showed higher prediction precision (R² = 0.98; P = 0.000004; n = 20) with average residual of 1.8 points. Predictive models including only ingredients from the same origin (e.g., marine-based, R² = 0.98; P = 0.033) also displayed low residuals. Since in vitro techniques have been usually validated through regressions against in vivo APD, the DH predictive capacity may depend on the consistency of the in vivo methodology. Regressions between APD and DH suggested a close relationship between peptide bond breakage by hepatopancreas digestive proteases and the apparent nitrogen assimilation in shrimp, and this may be a useful tool to provide rapid nutritional information.