Pea and wheat starch possess different processing characteristics and affect physical quality and viscosity of extruded feed for Atlantic salmon

The aim of the study was to investigate the effect of starch source, retention time in the preconditioner and screw speed (RPM) on physical quality of extruded fish feeds. The experiment was arranged in a three by two by two factorial design using three carbohydrate sources [wheat starch (WS), pea starch (PS) or a combination (WS_PS)], two retention times in the preconditioner [long (120 s) or short (62 s)] and two RPM in the extruder [high (300) or low (220)]. Physical quality was assessed by hardness, diameter, expansion ratio, Holmen durability (HDI), DORIS value (DV), oil absorption capacity, oil leakage and pasting viscosity. The results showed that retention time in the preconditioner only affected HDI and oil leakage. Long retention time improved HDI but caused a greater leakage. Changing screw speed from 220 to 300 RPM gave a greater expansion ratio, improved HDI and oil absorption. PS resulted in higher pasting viscosity, HDI and DV, but a generally lower hardness than WS. To conclude, PS and WS have different processing characteristics, and the conditions need to be adjusted according to the starch source used when producing extruded fish feed.     

Effect of selected feed meals and starches on diet digestibility in the mud crab,Scylla serrata

The present study examined the capacity of the mud crab, Scylla serrata to digest experimental diets that contained different animal and plant‐based feed meals or different levels or types of starch. The apparent dry matter digestibility (ADMD) coefficients for all feed meals tested in the first part of this study, except meat meal, were similar (78–88%). Crude protein digestibility (ACPD) coefficients for all feed meals were relatively high, with values ranging from 86% to 96%. Cotton seed meal, poultry meal, canola meal, fishmeal, soybean meal and lupin meal had similar gross energy digestibility (AGED) values (P>0.05) ranging from 84% to 89%. In the second part of this study, the impact of selected starches on the digestibility of fishmeal‐based formulated diets was assessed. The apparent starch digestibility (ASD) of wheat starch decreased significantly as the inclusion level was increased from 15% to 60%, however, there was no significant effect on ACPD values. At a 30% inclusion level, the ASD of diets containing different starches decreased in the order corn>wheat>potato=rice. Moreover, ACPD values were significantly higher (P<0.05) in the diets containing corn or rice starch than in those containing wheat or potato starches.     

池塘植藕对沉积物养分和酶活性的影响

为了揭示池塘种植莲藕对沉积物养分吸收及其养分转化相关酶的作用效果,将基本情况完全相同的黄颡鱼养殖池塘分为植藕组（Tf）和非植藕组（CK）,观察两组池塘在黄颡鱼苗种培育过程沉积物中养分和4种酶（脲酶、磷酸酶、蛋白酶、蔗糖酶）活性的变化特征。结果表明,与CK相比,Tf沉积物中的TN、NH4+—N和NO3-—N在莲藕苗期后均显著降低,在莲藕休眠期分别降低了8.5%、54.1%和52.7%,其中NH4+—N减少是沉积物中TN降低的主要原因;从莲藕苗期至花果期TP明显下降,最大降幅达22.6%;苗期后有机质开始显著降低,休眠期相较未植藕池塘降低8.4%。对两组池塘而言,沉积物的酶活性均呈现先增加后降低的变化趋势,Tf沉积物中4种酶的平均活性均高于CK,酶活性的差异在莲藕苗期和休眠期达显著水平（P < 0.5）。分析表明,4种酶之间存在着显著正相关关系（P< 0.5）,脲酶、磷酸酶和蔗糖酶活性与沉积物中NH4+—N的含量呈显著负相关,蛋白酶活性与沉积物中NO3-—N的含量呈显著正相关。     

鲢鱼糜与淀粉复合系统的微波糊化特性

在2 450 MHz频率的微波处理条件下,为了考察添加鲢鱼糜对小麦粉面团糊化的影响,将小麦粉、鲢鱼糜、NaCl和去离子水按比例混合制成鲢鱼糜面团,面团中鲢鱼糜含量分别为0%,10%,20%和30%(w/w,质量百分比),对样品面团中淀粉的介电特性和糊化特性进行研究。结果表明,对于相同尺寸的面团样品,添加鲢鱼糜可改善面团样品在电磁场中的加热均匀性。随着温度的升高,面团的介电常数和介电损失率分别在20~23和9~12内波动并呈下降趋势,微波的穿透深度因淀粉的糊化略有上升。淀粉的糊化速率随温度的升高而下降。降低样品中淀粉的含量,会使面团糊化活化能由113.54 kJ/mol下降至59.96 kJ/mol。     

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.     

Characterization and Film-Forming Properties of Gelatins from Whitemouth Croaker (Micropogonias furnieri) Skin and Bones

The Whitemouth croaker (Micropogonias furnieri), due to its abundance, is considered one of the most traditional and important species fished in the coastal waters and estuaries of South America. The aim of this work was to produce biopolymeric films of gelatins obtained from skin and bones of Whitemouth croaker. The fish gelatins were characterized through the yield, chemical composition, physiochemical, and rheological properties. The films were characterized by tensile strength (TS), elongation at break (EAB), water vapor permeability (WVP), thermogravimetric analysis (TGA), Fourier transform infrared spectroscopy (FT-IR), and optical properties. The values of protein yield, hydroxyproline content, gel strength, melting temperature, gelling temperature, and viscosity of the skin gelatin were higher than the values of the bone gelatin. The films obtained of skin gelatin showed all properties and thermal analysis superior in relation to the films of bone gelatin; this can be justified by the best physicochemical and rheological characteristics of the skin gelatin.     

The carbohydrate catabolism of <Emphasis Type="Italic">Zostera marina</Emphasis> influenced by lower salinity during the pre-germination stage

The distribution of starch granules in ungerminated seeds of Zostera marina was examined by electron microscopy and histochemistry. Quantitative changes during germination in starch and sugars [glucose/maltosaccharides (MS), sucrose, and fructose] were examined in the seeds using biochemical methods. At natural seawater salinity (30.2 psu), the number of starch granules and the amount of starch markedly decreased, resulting in no increase in the sugar content in the embryos during the early germination stage. A substantial increase in sugars in the shoots occurred after the development of true leaves, probably due to photosynthetic activity in the green true leaves. At natural seawater salinity, the amount of starch did not significantly change during the initial 14 days of germination. In contrast, at lower salinities, starch levels decreased significantly from day 0 to day 6, resulting in higher levels of glucose/MS and fructose in the basal hypocotyls. These results suggest that compared with the salinity of natural seawater, lower salinity may interfere with starch catabolism in seeds, thereby causing the seed coat to break open earlier.     

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.     

Utilization of different raw and pre-gelatinized starch sources by juvenile yellowfin seabream Sparus latus

Raw corn starch (RCS), raw tapioca starch (RTS), raw potato starch (RPS), pre‐gelatinized corn starch (PCS), pre‐gelatinized tapioca starch (PTS) and pre‐gelatinized potato starch (PPS) were evaluated as starch sources in diets for yellowfin seabream Sparus latus in a 56‐day growth trial. Seven isonitrogenous semi‐purified diets comprising a non‐starch cellulose control diet and the six different starch sources holding 200 g kg⁻¹ starch each were prepared and fed to triplicate groups of juvenile yellowfin seabream S. latus. Fish were fed for 8 weeks. Weight gain (WG) and specific growth rate (SGR) for fish fed RCS, RTS and RPS diets were equal, as well as for fish fed PCS, PTS and PPS diets, but values in groups fed the raw starch sources were significantly higher compared with fish fed the pre‐gelatinized starches. Feed efficiency and protein efficiency ratio in fish fed different starch source diets showed no significant differences but were significantly higher than those fed a non‐starch control diet. Protein productive value was improved by starch incorporation to diets. PCS, PTS or PPS groups showed lower feed intake compared with RCS, RTS or RPS groups, and the differences were significant between PCS, PPS and RCS, RPS groups. Whole‐body protein and ash contents and muscle compositions were not affected by different starch sources. Whole‐body and liver lipid contents, liver moisture and glycogen contents were significantly affected by starch source. Values of hepatosomatic index, intraperitoneal fat ratio, viscerosomatic index and condition factor did not vary between experimental treatments. Plasma total protein concentration for RCS, RTS or RPS fed fish was significantly higher than that for PCS, PTS or PPS fed fish, but significantly lower than that for non‐starch fed fish. Plasma cholesterol and triacylglycerol concentrations were unaffected by starch source, but were significantly higher in fish fed the non‐starch control diets. Plasma glucose concentrations in all dietary groups were relatively stable. In conclusion, raw corn, tapioca and potato starches at a 200 g kg⁻¹ inclusion level were well utilized as energy sources by yellowfin seabream, which was evidenced by better WG and SGR. Pre‐gelatinization of the starches had no positive effect on starch utilization.     

Effect of dietary starch source (normal versus waxy) and protein levels on the performance of white sea bream Diplodus sargus (Linnaeus) juveniles

An experiment was performed to evaluate the growth performance and feed utilization of white sea bream juveniles (initial weight, 14 g) fed diets of cornstarch of different origins (normal and waxy). Four experimental diets were formulated to be isolipidic and to contain normal and waxy starch (26% or 42%) at two protein (36% and 48%) levels. The growth trial lasted 15 weeks and, at the end of the trial, there were no differences in the growth rate among groups. At the highest dietary starch level – but not at the lowest level – the feed efficiency ratio and PER were significantly lower in fish fed the waxy starch diet. Protein efficiency ratio and N retention (% N intake) were not affected by starch source but were significantly higher in the diets with a lower protein content. No differences in energy retention (% energy intake) were observed among groups. Except for the protein content, which was significantly higher in fish fed diets with a high protein level, no other differences were observed among groups in whole‐body composition. Hepatosomatic Index (HSI) was significantly higher in fish fed high‐starch diets, but there were no differences in visceral indices among groups. The apparent digestibility coefficients of protein and energy were not affected by the dietary starch level, but were significantly lower in diets including waxy starch. Glutamate dehydrogenase activity was higher in fish fed high‐protein diets, but it was not affected by dietary starch source. Alanine aminotransferase and aspartate aminotransferase activities were not different among groups. Glucose 6‐phosphate dehydrogenase, malic enzyme and fatty acid synthetase activities were not affected by the dietary starch level, but were significantly lower in fish fed waxy starch. The results of this study indicate that diets for white sea bream juveniles may include up to 42% starch without negative effects on fish performance. Moreover, normal starch appears to be more efficiently used as an energy source than waxy starch.     

Effect of gelatinization degree and inclusion level of dietary starch on the characteristics of digesta and faeces in Nile tilapia (Oreochromis niloticus (L.))

Higher faeces removal efficiency can help and reduce the negative impact of faecal waste on water quality and on the environment. Physicochemical properties of feed ingredients/nutrients may change the faeces characteristics and the ratio of removed to non-removed solids. The aim of this study was to assess what physicochemical properties of the diet (viscosity, fermentation and dry matter) influence faeces characteristics and faeces removal using Oreochromis niloticus (L.) as the test animal. Four experimental diets were formulated by the addition of two types of starch differing in gelatinization degree (gelatinized and native) and two levels (high and low) of starch to a basal diet according to a 2 × 2 factorial design. The diets were assigned to 16 tanks with 40 fish each, with four replicates for each diet. Replacement of native starch by gelatinized starch improved faeces removal rate, growth and digestibility (P < 0.01), but reduced fermentation (P < 0.05) at the end of the intestine. Addition of gelatinized starch did not change viscosity and dry matter of the digesta at the end of the intestine. A high level of starch in the diet also increased digestibility, growth and faeces removal percentage (P < 0.05). Fermentation and dry matter content at the end of the intestine were not influenced by a high starch diet, but viscosity was higher at the high level of starch inclusion. Volatile fatty acid levels in the stomach of Nile tilapia were high in the treatments with gelatinized starch. In conclusion, intestinal fermentation induced by native starch had a negative impact on faeces removal efficiency. A higher inclusion level of starch resulted in a higher viscosity of the digesta, leading to higher faeces removal efficiency.     

大口黑鲈饲料中适宜的淀粉源及添加水平

以4种淀粉,蜡质玉米淀粉(L)、高直链玉米淀粉(Z)、小麦淀粉(X)和木薯淀粉(M),分别以5%和10%的添加量配制了8种等氮和等能(CP 48%,GE 18.5 MJ/kg)的饲料(L5、L10、Z5、Z10、X5、X10、M5和M10)。用上述饲料饲养初始体重为(23.46±0.19)g的大口黑鲈45 d,以评定大口黑鲈饲料的适宜淀粉源及添加水平。结果显示,饲料中淀粉的添加水平和淀粉源对大口黑鲈的生长、饲料利用、体组成和非特异性免疫指标均有显著影响。随着同一种淀粉的添加量从5%升至10%,L10、X10和M10组实验鱼的特定生长率和摄食率显著降低,但饲料效率和蛋白质效率显著升高,而Z5和Z10组间的上述指标的差异不显著;L10、X10和M10组的肝体比、脏体比和肝糖原含量均显著升高,但Z5和Z10组间的脏体比差异不显著;全鱼和肝的脂肪含量及肝的蛋白质含量均显著降低;L10组的红细胞数和红细胞压积、Z10组的血清甘油三酯及X10组的红细胞压积和血清甘油三酯水平显著降低;Z10组的血清补体活性显著降低;L5、Z5、X5和M5组的餐后3~12 h的血糖水平各自低于L10、Z10、X10和M10组。不同的淀粉源在相同的添加量的情况下,Z5组的淀粉表观消化率和肝体比显著地低于L5、X5和M5组,而脂肪沉积率显著高于L5、X5和M5组;M5组的蛋白质表观消化率显著低于L5、Z5和X5组;Z10组的淀粉表观消化率、肝体比、脏体比和肝糖原含量显著低于L10、X10和M10组,而脂肪沉积率显著高于L10、X10和M10组;M10组的蛋白质表观消化率显著低于L10、Z10和X10组。饲料中淀粉的添加水平和淀粉源对大口黑鲈的摄食率、特定生长率、蛋白质消化率、脂肪沉积率、肝体比、肝糖原含量、红细胞数、血清甘油三酯含量和血清补体活性均有显著的交互作用。本研究表明,饲料的淀粉源和水平对大口黑鲈的生长、体组成、血液学指标、餐后血糖和非特异性免疫指标均有不同程度的影响,饲料中添加5%的蜡质玉米淀粉、高直链玉米淀粉、小麦淀粉和木薯淀粉均无妨碍,但添加10%的淀粉水平唯有高直链玉米淀粉较为合适。     

不同小麦淀粉和脂肪水平对大黄鱼的生长性能、饲料利用及糖代谢关键酶活力的影响

为探讨饲料中添加不同小麦淀粉和脂肪水平对大黄鱼幼鱼生长、饲料利用以及糖代谢关键酶活力的影响,进行了为期8周的生长实验。设计了3个小麦淀粉水平(5%、10%和30%)和2个脂肪水平(5%和10%)的3×2的两因子实验,配制了6种等氮的饲料,分别喂养平均体质量为(6.75±0.12)g的大黄鱼幼鱼。结果显示,饲料中小麦淀粉和脂肪水平对大黄鱼增重率(WG)、特定生长率(SGR)、饲料效率(FE)、成活率(SR)、肝体比(HSI)和肥满度(CF)无显著交互作用,对脏体比(VSI)有显著交互作用。在同一脂肪水平下,淀粉水平为30%组WG和SGR显著高于10%淀粉组。不同小麦淀粉和脂肪水平对肝糖原含量无显著交互作用,而对肌糖原含量有显著交互作用,在饲料脂肪水平为5%时,30%小麦淀粉水平下的肝糖原含量显著高于10%和20%淀粉水平,10%淀粉水平下的肌糖原含量显著高于20%和30%淀粉水平;在脂肪水平为10%时,10%淀粉水平下的肝糖原含量显著高于20%和30%淀粉水平,而30%小麦淀粉水平下的肌糖原含量显著高于10%和20%淀粉水平。小麦淀粉和脂肪水平对血清中谷丙转氨酶(ALT)、谷草转氨酶(AST)、总胆固醇(TC)和葡萄糖(GLU)含量无显著交互作用,对总蛋白(TP)和甘油三酯(TG)交互作用显著。不同小麦淀粉和脂肪水平对肝脏脂肪酶活性有显著的交互作用,对淀粉酶活性无显著交互作用;同一脂肪水平下,脂肪酶的活性随着淀粉水平的升高而升高,同一饲料淀粉水平下,饲料脂肪水平为10%组的脂肪酶活性显著高于5%组。不同小麦淀粉和脂肪水平对肝脏丙酮酸激酶(PK)的活性有显著的交互作用,而对葡萄糖激酶(GK)、磷酸果糖激酶(PFK)、磷酸烯醇式丙酮酸羧激酶(PEPCK)、1,6-二磷酸果糖酶(FBPase)和6-磷酸葡萄糖酶(G6Pase)的活性均无显著交互作用。研究表明,当饲料脂肪水平为5%时,大黄鱼能够通过调节糖酵解关键酶活性及肝糖原含量来维持血糖平衡,改善对小麦淀粉的利用能力;而当脂肪水平为10%时,大黄鱼对小麦淀粉的利用能力降低。     

Growth performance,haematology and intestinal histo‐morphology of Nile tilapia fed on Indian Lotus (Nelumbo nucifera Gaertn.) leaf powder at different concentrations

Indian lotus, Nelumbo nucifera (Gaertn.) is a valued medicinal plant that exhibits several pharmacological properties. The present work aimed to investigate the effect of Indian lotus as a feed supplement on the growth performance, haematological and biochemical indices, and intestinal histo‐morphology of Nile tilapia (Oreochromis niloticus L.). The fish were randomly distributed into four groups and fed on a basal diet containing Indian lotus leaf powder at different concentrations (0, 0.1, 0.2 and 0.4%) for up to 60 days. The results elucidated that Indian lotus supplemented diets (0.2% and 0.4% followed by 0.1%) significantly improved weight gain, specific growth rate (%) and feed conversion ratio (p < .05). The feed intake was significantly increased in the fish fed on the Indian lotus supplemented diets in a dose‐dependent manner (p < .05). However, Indian lotus had no significant effect (p > .05) on survival rate, total erythrocytes (RBCs) count, haemoglobin (Hb) and hematocrit value (PCV, %) except a significant reduction on Hb content of the fish fed on 0.2% Indian lotus and a significant increase in PCV (%) in the fish fed on 0.1% Indian lotus (p < .05). The total leucocytes (WBCs), neutrophils and lymphocytes counts displayed significant elevations in the fish fed on the Indian lotus diets especially at 0.2% and 0.4%, whereas significant reduction in neutrophils count in the fish fed on 0.1% Indian lotus (p < .05) was observed. The serum glucose was significantly decreased in the fish fed on Indian lotus (0.1% and 0.2%), whereas cholesterol and triglycerides were markedly increased in the fish fed on the Indian lotus supplemented diets (p < .05). Moreover, the intestinal villous heights and the numbers of goblet cells and intraepithelial lymphocytes (IEL) were significantly boosted in all parts of the intestine in all Indian lotus diet groups as compared with the control group. However, as an exception, villous heights in the middle part of the intestine in the fish fed on 0.1% and 0.4% diets (p < .05) were not affected. In the proximal part, the villous heights and the numbers of goblet cells were markedly increased in fish fed on 0.2% and 0.4% diets followed by 0.1% diet. The fish fed on 0.2% lotus supplemented diet followed by 0.1% and 0.4% supplemented diets exhibited significant elevations in villous heights in the distal part and the numbers of goblet cells in the middle part of the intestine. There were no significant differences between the fish fed on the supplemented diets in the numbers of goblet cells in the distal part and the numbers of IEL in the proximal and middle parts (p > .05). In the distal part, the numbers of IEL revealed a significant elevation in 0.4% lotus supplemented diet followed by 0.1% and 0.2% lotus supplemented diet groups (p < .05). Therefore, this study indicates the advantageous effect of the Indian lotus leaves as a natural feed additive for improving growth, intestinal structure and hence, health status of Nile tilapia.     

高温胁迫对仿刺参抗氧化酶等指标的影响

在15、18、21、24、27、30℃水温下,分别制备仿刺参福建连江群体和辽宁大连群体的体腔和内脏团提取液,测定超氧化物歧化酶、过氧化氢酶、谷胱甘肽过氧化物酶、乳酸脱氢酶、碱性磷酸酶活力及丙二醛含量。试验结果显示,仿刺参连江群体内脏团提取液超氧化物歧化酶、过氧化氢酶、谷胱甘肽过氧化物酶和乳酸脱氢酶活力最大时的水温比大连群体分别提高了3~9℃;高温(24、27、30℃)胁迫下,连江群体体腔和内脏团提取液超氧化物歧化酶、过氧化氢酶、乳酸脱氢酶活力均极显著高于大连群体(P0.01),其内脏团提取液谷胱甘肽过氧化物酶活力亦极显著高于大连群体(P0.01),其体腔液谷胱甘肽过氧化物酶活力在24℃和30℃时极显著高于大连群体(P0.01);仿刺参连江群体和大连群体体腔液碱性磷酸酶活性均在15℃时最大,内脏团提取液的碱性磷酸酶活性则均在18℃时最大;连江群体仿刺参体腔和内脏团提取液丙二醛含量在18~30℃下均显著低于大连群体(P0.05,P0.01)。研究表明,福建连江夏季高温驯化的仿刺参子二代群体,在高温胁迫试验中,其体腔和内脏团提取液中超氧化物歧化酶、过氧化氢酶、谷胱甘肽过氧化物酶、乳酸脱氢酶、碱性磷酸酶活力显著高于大连群体,丙二醛含量则显著低于大连群体,这些酶耐热性的提高,有利于仿刺参机体清除因高温胁迫产生多余的自由基,减少机体因高温胁迫造成的损害。     

Identification of digestible carbohydrate sources for inclusion in formulated diets for juvenile spiny lobsters, Jasus edwardsii

Carbohydrates are a key ingredient in crustacean formulated diets because of their potential to greatly improve production efficiency. For the culture of spiny lobsters where daily food intake is limited, carbohydrates have the potential for delivering a low cost source of energy that could spare protein for growth. Therefore, the digestibility of different carbohydrate sources including refined sugars, mussel glycogen, algal polysaccharides, carboxymethyl cellulose (CMC) and starches (i.e., native, dextrinised, gelatinised) were assessed in juvenile spiny lobster (30–60 g). This was done by measuring the rate of carbohydrate hydrolysis in vitro using enzyme homogenates and postprandial haemolymph glucose concentrations following ingestion of semi-purified diets containing different carbohydrate levels and sources. Fresh mussel gonads and a practical formulated diet were also included for comparison. Storage polysaccharides (i.e., gelatinised starches, dextrin, mussel glycogen) and the structural polysaccharide CMC were the best digested carbohydrate sources in vitro. CMC was more digestible than the algal polysaccharides, agar and alginate, and therefore may have potential as a binding agent in formulated diets for J. edwardsii. The poor hydrolysis of sucrose and trehalose suggests that their use as an energy source might be limited in J. edwardsii. Native wheat starch was the best digested among the various plant starches tested. Gelatinisation of starches markedly improved their digestibility suggesting that pre-treatment of the dietary starch source would have a beneficial influence on the digestibility of diets for J. edwardsii. Consumption of the semi-purified diets (i.e., 1% BW) containing the digestible starch sources (i.e., 27% dry weight), as well as the practical diet, resulted in high haemolymph glucose concentrations (> 5 mmol l^− 1) and a prolonged hyperglycaemic response (> 24 h) suggesting that these carbohydrate sources are well digested and absorbed, but possibly poorly utilised. In contrast, the fresh mussel gonad diet (i.e., 27% glycogen by dry weight) appeared to be better utilised (reduced glycaemia after 12 h). A lower inclusion level (i.e., 7%) of gelatinised maize starch reduced the peak (1.87 mmol l^− 1) and extent (12 h) of the glycaemic response. Using lower inclusion levels (< 27%) of the rapidly digested starches (i.e., gelatinised, dextrinised) identified in this study, or incorporating digestible carbohydrate sources resulting in slower appearance of haemolymph glucose (i.e., native wheat starch, CMC), in formulated diets may have the potential to improve their utilisation for growth of juvenile spiny lobsters.     

Effects of dietary carbohydrate level on growth and body composition of juvenile tilapia, Oreochromis niloticus×O. aureus

A growth trial was conducted to feed juvenile tilapia (initial weight, 9.1±0.1 g), Oreochromis niloticus×O. aureus, isonitrogenous diets for 8 weeks. Six diets were formulated containing 29% crude protein from casein and gelatin, 10% crude fat from soybean oil and refined soybean lecithin and varying levels of corn starch ranging from 6% to 46% at increments of 8%, with corresponding energy to protein (E/P) ratios of 35.6, 37.9, 40.2, 42.5, 44.8 and 47.1 kJ g^?1. Weight gain (WG), specific growth rate, feed efficiency ratio and protein efficiency ratio were significantly higher in fish fed diets with starch ≥22% (or E/P ratio ≥40.2 kJ g^?1) than in fish fed diets with 6% or 14% starch (or E/P ratio of 35.6 or 37.9 kJ g^?1). No further improvement was measured when dietary starch content increased beyond 22%. Body protein retention showed the same general pattern as WG, and was highest in fish fed the 22% starch diet. Body composition was significantly affected by dietary starch level. Fish fed diets with starch ≥30% had significantly higher lipid content than fish fed diets with 6% or 14% starch. Ash content was negatively correlated with starch inclusion level, but moisture and protein contents did not show discernible trends among treatments. Results indicate that hybrid tilapia can utilize 46% dietary starch without growth retardation, while 22% starch in feed for juvenile tilapia containing 29% protein and 10% lipid, or an E/P ratio of 37.9 kJ g^?1 is optimal.     

Apparent Digestibility of Gross Nutrients from Feedstuffs in Extruded Feeds for Rainbow Trout,Oncorhynchus mykiss

Abstract.— The current experiment was performed to determine apparent protein and energy digestibility coefficients of feed ingredients by the fecal stripping technique using extruded diets. The ingredients tested included five fish meals, three terrestrial animal by‐products, five plant protein concentrates, four plant meals, and seven low‐protein plant ingredients. Protein digestibility differed among fish meals and ranged from 90% for fair and average quality menhaden meal to 97% for anchovy meal. Protein apparent digestibility coefficients (ADCs) in plant concentrates ranged from a low of 89% for rice protein concentrate to a high of 100% for wheat gluten meal. Apparent protein digestibility was lower in plant meals than fish meals with a low of 70% for flaxseed meal to a high of 89% for soybean meal. Low‐protein plant meals had generally lower protein ADC from 64% for rice bran to 85% for whole wheat. A similar pattern for energy ADCs was observed; ADCs ranged from 106% for anchovy meal to 32% for whole wheat. In the current trial, divergent protein and energy ADC values were obtained most notably in ingredients known to be high in fiber or have very high starch content. The comparability of ingredients/diets processed by cold pelleting or extrusion thus appears questionable at this juncture.     

不同种类淀粉对草鱼生长、肠系膜脂肪沉积和鱼体组成的影响

将试验草鱼随机分配在 12个水族箱中 ,每箱放鱼 30尾 ,分别以玉米淀粉、小麦淀粉、水稻淀粉为糖源配制 3种试验饲料 ,饲养初始体重为 (8.49± 0 .0 4)g的草鱼 80d ,观察不同种类淀粉饲料对草鱼生长、肠系膜脂肪沉积和鱼体组成的影响。每种饲料设 3个平行组 ,日投喂率按鱼体重的 3%计算。试验结果显示 :尽管草鱼对糖的表观消化率以小麦淀粉组最高 ,但摄食小麦淀粉饲料的草鱼与摄食玉米淀粉和水稻淀粉饲料的草鱼在生长上并无显著性差异。然而小麦淀粉组和玉米淀粉组的内脏比、肝胰脏脂肪含量、血浆甘油三酯水平以及肠系膜脂肪占鱼体的百分比显著高于水稻淀粉组 (P <0 .0 5 )。鱼体营养成份组成除了水稻淀粉组全鱼脂肪含量相对低于玉米淀粉组和小麦淀粉组之外 ,其它成份没有太大的差异。     

饲料中不同蛋白质和淀粉水平对斜带石斑鱼生长性能和肝脏相关代谢酶活性的影响

为了探讨饲料蛋白质和碳水化合物对斜带石斑鱼的互作效应,实验采用3×3因子设计,配制蛋白质水平(P)为38%、45%和52%,淀粉水平(S)为10%、20%和30%的9种实验饲料,分别饲喂斜带石斑鱼56 d。结果显示,38%粗蛋白与10%淀粉饲料组(38P/10S饲料组)增重率显著低于其他各组,52P/10S组增重率最高,但与45P/20S、45P/30S、52P/20S组差异不显著。增加饲料蛋白质或淀粉水平显著增加饲料效率、鱼体蛋白质与脂肪含量及肝糖原肝脂含量,而降低摄食率和鱼体水分含量。增加饲料蛋白质水平降低蛋白质效率,但增加淀粉水平却增加蛋白质效率及肝体比与脏体比。饲料蛋白质水平和淀粉水平对鱼体灰分含量无明显影响。肝中肝酯酶、脂蛋白酯酶、脂肪酸合成酶、谷丙转氨酶和谷草转氨酶活性均随蛋白质或淀粉水平的升高呈显著上升趋势。增加饲料蛋白质水平显著降低肝中葡萄糖-6-磷酸酶活性,而增加肝中苹果酸酶活性,但对肝中葡萄糖激酶、丙酮酸激酶、磷酸果糖激酶、磷酸烯醇式丙酮酸羧激酶和葡萄糖-6-磷酸脱氢酶活性没有明显影响。增加饲料淀粉水平显著增加肝中葡萄糖激酶、丙酮酸激酶、磷酸果糖激酶、葡萄糖-6-磷酸脱氢酶和苹果酸酶活性,但显著降低磷酸烯醇式丙酮酸羧激酶和葡萄糖-6-磷酸酶活性。上述结果显示,斜带石斑鱼的生长和肝脏代谢明显受饲料蛋白质和淀粉水平的影响,其中,糖代谢酶活性受淀粉水平的影响较大,而受饲料蛋白质水平的影响较小,斜带石斑鱼生长适宜的饲料蛋白质和淀粉水平分别为45%和20%。