南方鲇的营养学研究:Ⅰ.人工饲料的消化率

采用循环水养殖系统在２７．５℃条件下,用人工饲料持喂养南方鲇（Ｓｉｌｕｒｕｓ ｍｅｒｉｄｉｏｎａｌｉｓ Ｃｈｅｎ）幼鱼６周。以三氧化二铬（Ｃｒ２Ｏ３）为指示物,测定了蛋白质含量为３５％至６０％（变化梯度为５％）的６种等能（２０ｋＪ／ｇ）试验饲料的消化率,实验结果表明,饲料蛋白南水平由３９．８６％升至５５．７３％时,饲料干物质表观消化率（Ｄｄｍ）、蛋白质表观消化率（Ｄｐ）、脂肪表观消化率（Ｄ１）、能     

饲料碳水化合物水平对南方鲇生长的影响

2002年6—8月对南方鲇(SilurusmeridionalisChen)(初始体重12.93±0.13g)进行人工配合饲料的喂养实验。实验以白鱼粉、玉米油、糊化玉米淀粉分别作为蛋白质、脂肪和碳水化合物(CBH)原料。配制等蛋白质(含量为40%),等脂肪(含量为10%),不同CBH梯度的6组饲料,饲料CBH水平分别设计为0%,6%,12%,18%,24%,30%。实验每水平设4个重复,采用室内循环水养殖系统,在27.5℃下以饱足日粮水平喂养8周。实验结果表明:随着饲料淀粉水平的增加,摄食率和生长率呈先增加后降低的趋势;当饲料CBH水平不超过18%时,不会对饲料成分的消化率产生显著影响,但添加量超过18%会降低CBH的消化率。综合实验结果分析:南方鲇生长的最适CBH为12%—18%。     

条斑紫菜中R－藻红蛋白的生化特性

条斑紫菜的Ｒ－藻红蛋白（Ｒ－ＰＥ）,在ＣＭ－５２柱上用含８ｍｏｌ／Ｌ脲的０．０２ｍｏｌ／Ｌ乙酸铵缓冲液（ｐＨ＝５．０５）洗脱,观察到３条色带,经吸收光谱测定表明,它们分别是α、β、γ亚基。用ＳＤＳ－ＰＡＧＥ测定的α、β和γ亚基分子量分别是１７．０ｋｄ,１８．０ｋｄ和３１．７ｋｄ。Ｒ－ＰＥ中亚基的摩尔比是６α：６β：１γ。条斑紫菜的Ｒ－ＰＥ最稳定的聚集态分子量是２２９ｋｄ。各亚基的发色团含量：α亚基含２个藻红胆素（ＰＥＢ）,β亚基含１个ＰＥＢ和０．５个藻尿胆素（ＰＵＢ）,γ亚基含２个ＰＥＢ和３个ＰＵＢ。结合Ｒ－ＰＥ和各亚基的氨基酸组成分析,条斑紫菜的Ｒ－ＰＥ亚基组成是（αβ）６γ。     

P物质对GABAA和GABAB受体介导的DRG神经元膜反应的调制作用

实验在幼年大鼠ＤＲＧ标本上进行。应用细胞内记录观察了ＳＰ对ＧＡＢＡ反应的调制作用。结果证明：（１）单独滴加ＳＰ（５×１０（－６）－４×１０（－５）ｍｏｌ／Ｌ）或浴槽灌流ＳＰ（１０（－６）－５×１０（－６）ｍｏｌ／Ｌ）不引起膜电位的改变或仅有轻微的去极化,但却能使ＧＡＢＡ引起的去极化反应减小５０．８±２０．２％（±ＳＤ）（２０／３０）;（２）单独滴加ＳＰ可使多数受检细胞ＡＰＤ５０延长２８．７±９．１％（±ＳＤ）（１０／１８）;（３）在预加ＳＰ后,能使ｂａｃｌｏｆｅｎ所引起的ＡＰＤ５０缩短效应（２０．６±２．９％,±ＳＤ）完全消除（４／１２）或翻转成ＡＰＤ（５０）延长１９．３±８．９％（±ＳＤ）（８／１２）;（４）预加ＧＡＢＡＢ受体激动剂ｂａｃｌｏｆｅｎ（１０（－４）－１０（－３）ｍｏｌ／Ｌ）３０—９０ｓ后明显地抑制ｍｕｓｃｉｍｏｌ（１０－４－１０－３ｍｏｌ／Ｌ）引起的去极化反应,其抑制效应达５４．４±１８．８％（±ＳＤ）（１７／２０）。由于ＤＲＧ神经元的胞体通常可用来作为研究初级传入终末的模型,因而本文实验结果提示：介导伤害性刺激信息的Ｐ物质在背角的释放,可能作用于初级传入终末,从而产生对抗ＧＡＢＡ介导的突触     

豚鼠腹腔神经节迟慢兴奋性突触后电位与5－HT和P物质的关系

应用细胞内记录,研究了豚鼠腹腔神经节（ＣＧ）细胞非胆碱能迟慢兴奋性突触后电位（ＬＳ－ＥＰＳＰ）与５－羟色胺（５－ＨＴ）及Ｐ物质（ＳＰ）的相互关系。当重复电刺激内脏大神经（ＳＮ）时,有７８．２％的细胞（１６１／２０６）在动作电位发放后出现ＬＳ－ＥＰＳＰ,灌注或压力注射５－ＨＴ或ＳＰ,分别在６８．５％的细胞（１０２／１４９）及５２．１％的细胞（９８／１８８）上引起５－ＨＴ或ＳＰ去极化反应,两者差异非常显著（Ｐ＜０．０１）;大部分具有ＬＳ－ＥＰＳＰ的细胞对５－ＨＴ（７３／８８,８３．０％）或ＳＰ（６８／１１４５９．６％）敏感,而不出现ＬＳ－ＥＰＳＰ的细胞仅有少数对５－ＨＴ（１０／２６,３８．５％）或ＳＰ（１１／３６,３０．６％）敏感,两类细胞的差异非常显著（５－ＨＴ：Ｐ＜０．０００１,ＳＰ：Ｐ＜０．０１）。上述结果支持５－ＨＴ与ＳＰ均作为递质参与ＬＳ－ＥＰＳＰ形成的观点。此外,在１３３个细胞上同时检测了５－ＨＴ与ＳＰ的作用,其中有６６个细胞（４９．６％）对５－ＨＴ及ＳＰ均敏感,提示在ＣＧ细胞,５－ＨＴ与ＳＰ之间可能存在某种机能联系。     

α_1肾上腺素能受体介导去甲肾上腺素促大鼠培养心肌细胞蛋白质合成效应

在无血清和含１．０％、５．０％血清培养的新生大鼠心肌细胞标本上,去甲肾上腺素（ＮＥ,２．０μｍｏｌ／Ｌ）使细胞蛋白质含量（Ｌｏｗｒｙ法）分别比相应对照组增加４０％、２６％、１９％（Ｐ均＜０．０１）;细胞３Ｈ－亮氨酸参入量与ＮＥ浓度呈正性剂量依赖性,最大效应浓度为２０．０μｍｏｌ／Ｌ;无血清培养体系中,０．２、２．０、２０μｍｏｌ／Ｌ的ＮＥ使参入量分别比对照增加１７．８％、３５３％、３７．７％;１．０％血清培养体系中分别比对照增加１６．２％、２７．９％、３１．６％（Ｐ均＜０．０５）;哌唑嗪（２．０μｍｏｌ／Ｌ）可阻断ＮＥ的促蛋白质合成作用,心得安（２．０μｍｏｌ／Ｌ）则无此效应。提示在无血清或低浓度血清培养体系中,ＮＥ可促进心肌细胞蛋白质合成,增加细胞蛋白质含量,该作用可能是通过α１肾上腺素能受体介导。     

P物质对大鼠DRG神经元胞体膜的作用

本文在大鼠ＤＲＧ神经元标本上应用细胞内记录,以确定ＳＰ对ＤＲＧ细胞的膜反应及其可能的离子机制。实验所测ＤＲＧ细胞静息膜电位为－５８．９±８．２ｍＶ（Ｘ±ＳＥ,ｎ＝８１）。传导速度：Ａ_（α／β）细胞为２０．４±４．８ｍ／ｓ（Ｘ±ＳＥ）,范围１４．１－２８．７ｍ／ｓ（４７／６０）;Ａδ及Ｃ类细胞为９．８±５．２ｍ／ｓ,范围１．２－１３．７ｍ／ｓ（１３／６０）。浴槽滴加ＳＰ（１０￣（－７）－３×１０￣（－４）ｍｏｌ／Ｌ）在大多数细胞可引起明显的膜去极化反应（５６／６０）。少数细胞对ＳＰ无反应（４／６０）。在ＳＰ去极化期间膜电导值有所增加,从平均值２．７２×１０￣（－８）ｍｈｏ增加２４．６％（ｎ＝３）。所测逆转电位值在＋４０－＋５０ｍＶ之间（ｎ＝３）。浊流平衡液（ＢＳＳ）中ＮａＣｌ以氯化胆碱置代,或用含ＴＴＸ（１０￣（－５）ｍｏｌ／Ｌ）的ＢＳＳ灌流,可使ＳＰ－去极化幅值大大减小但不能完全消除。而高（２０ｍｍｏｌ／Ｌ）和低（０ｍｍｏｌ／Ｌ）Ｃａ￣（２＋）的ＢＳＳ灌流时,使ＳＰ－去极化幅值相应的增加和降低。用含１０￣（－４）ｍｏｌ／ＬＣｄ￣（２＋）及１０￣（－２）ｍｏｌ／ＬＴＥＡ的ＢＳＳ灌流,均使ＳＰ－去极化明显减小。     

单宁酶的固定化及其在酯型儿茶素水解反应中的应用

采用自制的壳聚糖为载体对单宁酶（ＴＡ）固定化,ＴＡ与壳聚糖配比１：２．５,３０℃固定２ｈ,活力回收达２３．６％～３３．１％;偶联效率为８４．９％～８８．０％。固定化单宁酶（ＩＴＡ）的表观Ｋｍ值（以没食子酸丙酯为底物）为２２．２×１０－６ｍｏｌ／Ｌ,ＴＡ的Ｋｍ值（以没食子酸丙酯为底物）为１０×１０－６ｍｏｌ／Ｌ,ＴＡ和ＩＴＡ的最适反应温度分别为４０℃和５０℃;６０℃处理１５ｍｉｎ,残存活性分别为１３．６％和６０．３％。ＴＡ和ＩＴＡ的最适ｐＨ值分别为５．８和６．４;ＴＡ在ｐＨ４．８～７．８活力稳定,而ＩＴＡ活力稳定范围在ｐＨ４．８～６．８．ＩＴＡ作用于ＥＧＣＧ的半衰期为７８．７ｈ,ＥＧＣＧ水解率达９０．３％。对茶多酚提取物进行水解,其所含的酯型儿茶素ＥＧＣＧ和ＥＣＧ水解率分别为９６．４％和９６．８％,非酯型儿茶素ＥＧＣ和ＥＣ的含量显著增加。     

内皮素—1对大鼠排卵前卵泡颗粒细胞产生孕酮的影响

本文用离体细胞体外孵育法研究了内皮素－１（ＥＴ）对大鼠排卵前卵泡颗粒细胞孕酮生成的影响及其作用机理。结果发现,ＥＴ能显著抑制ｈＣＧ刺激下的孕酮产生,抑制作用在浓度为１０－８ｍｏｌ／Ｌ时,即有显著意义（Ｐ＜０．０５,ｎ＝６）,至１０－７ｍｏｌ／Ｌ时则有非常显著的意义（Ｐ＜０．０１,ｎ＝６）;不同浓度ＥＴ（１０－７—１０－７ｍｏｌ／Ｌ）,对颗粒细胞基础孕酮的产生无明显影响。进一步研究表明,ＥＴ对ｈＣＧ刺激下孕酮生成的抑制作用,在用免抗人内皮素抗血清（ＥＴ－Ａ）１：１０００及ｃＡＭＰ后能明显被逆转。实验中还观察到,ＥＴ使颗粒细胞ＬＨ／ｈＣＧ受体数下降,亲和力降低。本文结果提示,ＥＴ可能为卵巢内的一种局部调节肽,通过作用于ＥＴ受体,干扰ＬＨ／ｈＣＧ受体功能和ｃＡＭＰ生成而抑制颗粒细胞孕酮的产生。     

L－NNA和还原型Hb对SHRsp肠系膜动脉内皮依赖性舒张的影响

我们以往的工作证实成年自发高血压大鼠（ＳＨＲ与ＳＨＲｓｐ）肠系膜动脉由乙酰胆碱引起的内皮依赖性舒张（ＥＤＲ）减弱。为进一步探讨ＥＤＲ减弱的机制，本文观察了一氧化氮（ＮＯ）合成酶抑制剂左旋硝基精氨酸（Ｌ－ＮＮＡ）及ＥＤＲＦ灭活剂还原型血红蛋白（ＲＨｂ）对卒中易感型自发高血压大鼠（ＳＨＲｓｐ）与常压对照（ＷＫＹ）大鼠肠系膜动脉ＡＣｈ内皮依赖性舒张（ＥＤＲ）的影响。发现Ｌ－ＮＮＡ（１０（－３）ｍｏｌ／Ｌ）可使ＳＨＲｓｐ弱于ＷＫＹ的ＡＣｈＥＤＲ（１０（－８）－１０（－５）ｍｏｌ／Ｌ）的差异消失，ＲＨｂ（１０（－５）ｍｏｌ／Ｌ）则仅在１０（－７）－１０（－８）ｍｏｌ／ＬＡＣｈ时使ＳＨＲ（ｓｐ）肠系膜动脉ＥＤＲ弱于ＷＫＹ的差异消失。将ＷＫＹ在加入Ｌ－ＮＮＡ后的与加入ＲＨｂ后的ＡＣｈ（１０（－８）－１０（－５）ｍｏｌ／Ｌ）ＥＤＲ进行比较，无显著差异。而将ＳＨＲｓｐ在Ｌ－ＮＮＡ后的与ＲＨｂ后的ＡＣｈ（１０（－８）－１０（－６）ｍｏｌ／Ｌ）ＥＤＲ进行比较，则有显著差异。并且，ＳＨＲｓｐ的有内皮肠系膜动脉条对ＲＨｂ的敏感性与ＷＫＹ接近，对Ｌ－ＮＮＡ的敏感性则低于ＷＫＹ。表明高血压时肠系膜动脉内皮依赖性舒张减弱中，ＥＤＲＦ机制与     

Influence of dietary protein and lipid levels on growth, body composition and utilization efficiencies of Arctic charr, Salvelinus alpinus L.

Growth, body composition and feed utilization were evaluated for Arctic charr fed a control diet and nine practical diets formulated to contain three protein levels (34, 44 or 54%) at each of three lipid levels (10, 15 or 20%). Fish were raised for 24 weeks at 12° C. Increasing either dietary protein and/or lipid resulted in improved weight gain, feed efficiency and energy retained. Protein efficiency ratio and protein retained were directly related to dietary lipid and inversely related to dietary protein. A sparing effect of lipid on protein was evident where, at each protein level, Arctic charr utilized protein more efficiently with each increase in dietary lipid. Levels of 34% protein and/or 10% lipid were well below the requirements for Arctic charr (initial weight, 4.6 g). Within the range tested, the dietary combination of 54% protein with 20% lipid maximized weight gain and feed efficiency and resulted in fish with low liver and body lipid contents. However, if lowest feed cost per kg gain is an important factor, the 44% protein—20% lipid diet would be less expensive to use, although it results in a minor reduction in growth potential.     

Use of alternative protein sources for fishmeal replacement in the diet of largemouth bass (Micropterus salmoides). Part I: effects of poultry by-product meal and soybean meal on growth,feed utilization,and health

Five isonitrogenous and isocaloric diets [containing 54, 30, 15, 10, and 5% fishmeal crude-protein (CP), dry matter (DM) basis] were prepared by replacing fishmeal with poultry by-product meal plus soybean meal to feed juvenile largemouth bass (LMB, with an initial mean body weight of 4.9 g) for 8 weeks. All diets contained 54% CP and 13% lipids. There were four tanks of fish per treatment group (15 fish/tank). The fish were fed twice daily with the same feed intake (g/fish) in all the dietary groups. Results indicated that the inclusion of 15% fishmeal protein in the diet is sufficient for LMB growth. However, some of the fish that were fed diets containing ≤ 15% fishmeal CP had black skin syndrome (characterized by skin darkening and retinal degeneration, as well as intestinal and liver atrophies and structural abnormalities). The concentrations of taurine, methionine, threonine and histidine in serum were reduced (P < 0.05) in fish fed the diets containing 5, 10 and 15% fishmeal CP, compared with the 30 and 54% fishmeal CP diets. Interestingly, the concentrations of tyrosine and tryptophan in serum were higher in fish fed diets with ≤ 15% fishmeal CP than those in the 54% fishmeal CP group. These results indicated that 15% fishmeal CP in the diet containing poultry by-product meal and soybean meal was sufficient for the maximum growth and feed efficiency in LMB but inadequate for their intestinal, skin, eye, and liver health. A reduction in dietary methionine and taurine content and the possible presence of antinutritional factors in the fishmeal replacements diets containing high inclusion levels of soybean meal may contribute to black skin syndrome in LMB. We recommend that the diets of juvenile LMB contain 30% fishmeal CP (DM basis).

     

Growth and hepatic acetyl coenzyme-A carboxylase activity are affected by dietary protein level in European seabass (Dicentrarchus labrax)

Two trials were undertaken with European seabass (Dicentrarchus labrax) to estimate the protein requirements for maintenance and growth as well as the effect of dietary protein level on the activity of hepatic acetyl coenzyme-A carboxylase (ACoAC). Six diets were formulated to contain graded levels of protein (from 5 to 55% crude protein (CP)) at a constant (12%) lipid level. Three other diets were also formulated to contain 35, 45 and 55% CP, but with a higher lipid level (19%). Groups of 10 individually marked fish (IBW: 100 g) and groups of 8 fish (IBW: 160 g) were used in trial I and II, respectively. Fish were fed to visual satiety and intake was recorded. At the end of both studies, whole body, liver and plasma samples were withdrawn for analyses. Growth rate was improved with increasing dietary CP level. Despite not being the object of a statistical analysis, feed efficiency tended to be enhanced at higher dietary CP level and protein efficiency ratio tended to decrease with increased protein intake. The reduction of the dietary protein/energy ratio, due to the increase of dietary lipids further improved growth and feed utilisation. Data from both experiments indicate 4.5+/-0.5 g kg(-1) d(-1) as the daily protein intake for maximum N gain and 520+/-50 mg kg(-1) d(-1) as the maintenance needs for nitrogen balance. An increase of dietary CP level, up to 25%, increased ACoAC activity. A further increase in dietary CP level (35 to 55%) did not affect liver ACoAC activity. The increase in dietary lipid level depressed significantly liver ACoAC specific activity.     

Growth and feed utilization by F4 human growth hormone transgenic carp fed diets with different protein levels

The F₄ generation of human growth hormone (hGH) transgenic red common carp Cyprinus carpio had significantly higher growth rates than the non-transgenic controls. Protein and energy intakes were significantly higher in the transgenic carp than in the controls fed the 20% protein diet, but were not different between the two strains fed diets with 30 and 40% protein. Faecal protein loss, as a proportion of protein intake, was significantly lower in the transgenics than in the controls fed diets with 20 and 30% protein, but was not different between the two strains fed diet with 40% protein. Faecal energy loss, as a proportion of energy intake, was significantly lower in the transgenics than in the controls fed diet with 20% protein, but was not different between the two strains fed diets with 30 and 40% protein. Recovered protein, as a proportion of protein intake, was significantly higher in the transgenics than in the controls fed all diets, whereas recovered energy was significantly higher in the transgenic fish fed the 40% protein diet. For fish fed each diet, the transgenics had significantly higher body contents of dry matter and protein, but lower contents of lipid than the controls. It was concluded that transgenics were more efficient in utilizing dietary protein than the controls. At a lower dietary protein level, transgenics achieved higher growth rates mainly by increasing feed intake; at higher levels of dietary protein, transgenics achieved higher growth rates mainly through a higher energy conversion efficiency.     

饲料中不同蛋白、脂肪水平对春鲤生长、饲料利用和体成分的影响

研究旨在探讨洱海土著鱼类春鲤(Cyprinus longipectoralis)(初始体重0.55 g)对蛋白质和脂肪的需求量。实验采用3×3双因子设计,蛋白水平为33%、39%和45%,脂肪水平为5%、8%和11%,共9组等能饲料。实验在水温为(28±2)℃的室内微流水系统中进行,为期56d。实验结果表明:随着蛋白水平的提高,摄食率显著降低(P<0.05),饲料效率、能量沉积率、鱼体水分和脂肪含量显著升高(P<0.05),但特定生长率、蛋白质效率、蛋白沉积率、鱼体灰分含量和能值均无显著变化(P>0.05)。随着脂肪水平的提高,特定生长率、蛋白沉积率和鱼体蛋白含量显著下降,鱼体脂肪含量显著上升(P<0.05),而摄食率、饲料效率、能量沉积率、鱼体水分和灰分含量以及能值则无明显变化(P>0.05)。通过折线回归分析得出,当饲料中蛋脂比为7.30时,春鲤有最大的特定生长率。研究结果表明,春鲤饲料中适宜的蛋白和脂肪水平分别为33%—34%和4%—5%。     

不同蛋白质和脂肪水平对1龄团头鲂生长性能和体组成的影响

试验采用3×3因子设计,探讨了饲料中不同蛋白质和脂肪水平对1龄团头鲂[均重:(50.37±1.27)g]生长性能和体组成的影响。试验设3个蛋白质水平(25%、30%和35%)和3个脂肪水平(3%、6%和9%),共配制9组饲料。试验鱼饲养于网箱(规格为2 m×1 m×1 m)中,每天投喂3次,试验期为8周。结果表明:蛋白质和脂肪之间无交互作用存在(P>0.05)。蛋白质和脂肪水平对存活率无显著影响(P>0.05)。增重率、特定生长率和饵料系数显著受蛋白质和脂肪水平影响(P<0.05)。其中,25%蛋白组的增重率及特定生长率显著低于其他蛋白组(P<0.05),而6%脂肪组显著高于其他脂肪组(P<0.01)。尽管35%蛋白6%脂肪组的饵料系数最低,但与除了25%蛋白3%脂肪和25%蛋白9%脂肪这两组外的其他组相比,差异均不显著(P>0.05)。蛋白效率比和氮保留率随蛋白质水平的升高显著降低(P<0.05)。此外,蛋白效率比显著受脂肪水平的影响(P<0.05),以6%组最高。能量保留率随脂肪水平的升高显著升高(P<0.05)。鱼体肥满度随蛋白质和脂肪水平的升高显著升高(P<0.05)。腹脂率和肝体比随脂肪水平的升高显著升高(P<0.05),而受蛋白质水平的影响较小(P>0.05)。蛋白质水平对全鱼、胴体和肝脏的组成均无显著影响(P>0.05)。脂肪水平对全鱼水分、脂肪和能量有极显著影响(P<0.01),其中,全鱼水分含量随脂肪水平的升高显著降低(P<0.01),而脂肪和能量含量则显著升高(P<0.01)。胴体和肝脏水分、脂肪含量的变化趋势与全鱼基本一致。以上结果表明,1龄团头鲂的适宜蛋白质和脂肪水平分别为30%和6%,适宜蛋能比为18.21 g/MJ。     

Effect of dietary protein and carbohydrate levels on growth,nutrient utilization and body composition in fingerling rohu,Labeo rohita (Hamilton)

Twelve experimental diets (D‐1 to D‐12) in a 4 × 3 factorial design having four protein levels (25, 35, 40 and 45%) and three carbohydrate levels (15, 25 and 35%) were formulated and fed to fingerling rohu, Labeo rohita (5.48 ± 0.02 g) for 60 days in three replicates at 2% BW per day. The best performance of fish in terms of weight gain (%), specific growth rate (SGR; % per day), feed conversion ratio (FCR) and protein efficiency ratio (PER) was recorded with diet D‐9 containing 40% protein and 35% dextrin as a source of dietary carbohydrate. In general, lower protein consumption per kilogram BW was observed at all protein levels with the rise of the dextrin level. The apparent digestibilities of protein and lipid were not affected by the dietary treatments. At the end of the experiment the body composition of animals from all treatments showed lower percentages of moisture and higher percentages of protein as compared to the initial values. A consistent rise in protein retention efficiency was noted in fish fed diets with increasing dextrin levels. The highest protein sparing effect was found in fish fed the diet containing 40% protein and 35% dextrin.     

Growth performance and body composition of sub-yearling Persian sturgeon, (Acipenser persicus, Borodin, 1897), fed different dietary protein and lipid levels

In order to evaluate the protein and energy requirement of Persian sturgeon (Acipenser persicus) sub‐yearlings, eight experimental diets containing two protein levels (40% and 45%) and four lipid levels (10%, 15%, 20% and 25%) were tested. Sturgeons (W₀ = 136.8 g) were fed the experimental diets to satiation four times daily for 150 days, resulting in a final mean weight of 375.8 g. Growth was significantly affected by lipid content of the diets. At 40% protein level, weight gain and specific growth rate (% per day) were significantly improved (P < 0.05) by increasing the dietary lipid (energy) content. Protein efficiency ratio (PER) was significantly affected by different dietary treatments for each dietary protein level tested, reaching a mean value of 3.58 in fish fed high lipid diets and a PER of 2.77 in low lipid diets. Results obtained in the present study suggest that the optimum dietary protein content for Persian sturgeon is 40%, with an estimated optimum protein‐to‐energy ratio of 18–20 mg kJ⁻¹.     

Effects of dietary protein and lipid levels on growth and feed utilization of wild‐caught striped sea bream,Lithognathus mormyrus

A feeding trial was carried out to determine the effects of dietary protein and lipid levels on the growth performance and feed utilization of wild‐caught striped sea bream (Lithognathus mormyrus). The experimental fish were collected from a local lagoon (Çardak Lagoon, Çanakkale, Turkey), transferred to the Marine Net Cage Unit and fed by hand to apparent satiation with a commercial sea bream feed (Biomar; 42% crude protein, 16% crude lipid). Approximately 4 weeks were needed to acclimate the fish to farming conditions. No pathological signs were observed and no fish losses occurred during the adaptation period. For the test trials four test diets with different levels of protein and lipid were formulated [low protein and low lipid (LP:LL), low protein and high lipid (LP:HL), high protein and low lipid (HP:LL), and high protein and high lipid (HP:HL)] and fed to L. mormyrus (mean weight 85.0 ± 4.6 g SEM) in the net cages (Ø 2 m, depth 2.5 m) for 60 days. During the experiment water temperature varied between 21.1 and 26.4°C; dissolved oxygen 8.4–9.6 mg L^?1; pH 7.2–8.6; and salinity 23.3–25.6‰. Growth performances of fish fed high protein diets were higher compared to fish fed low protein diets, irrespective of the dietary lipid level (P < 0.05). Feed conversion ratio (FCR) and protein efficiency ratio (PER) were not influenced by dietary protein or lipid levels (P > 0.05). Preliminary results indicate that striped sea bream can be easily adapted to farming conditions in net cages, and that a diet containing 50% crude protein and 15% crude lipid (HP:LL) levels with 23.0 g protein MJ^?1 gross energy of protein/energy ratio would be suitable for striped sea bream growth.     

The IMTA-cultivated Chlorophyta Ulva spp. as a sustainable ingredient in Nile tilapia (Oreochromis niloticus) diets

Increasing levels of a mixture of Ulva spp. produced in an integrated multi-trophic aquaculture (IMTA) system were evaluated in Nile tilapia juveniles for partial replacement of dietary fish meal. A control diet (CTRL) was compared with three experimental diets containing 10 % (U10), 15 % (U15), and 20 % (U20) of Ulva spp. meal. Triplicate groups of fish (13 g initial body weight) were fed each diet for 63 days at 26 °C. Nutrient apparent digestibility coefficients and nitrogen retention efficiency did not vary significantly among diets. By the end of the trial, all groups of fish more than tripled their initial body weight. Specific growth rate and final body weight of U10 diet were similar to CTRL and significantly higher than U15 and U20 diets. Increasing Ulva dietary incorporation levels significantly increased feed conversion ratio (FCR), from 1.0 (CTRL) to 1.4 (U20). Fish fed with U10 diet had the highest protein efficiency ratio and nitrogen retention efficiency allowing this fish to growth and reach a final body weight similar to the CTRL group. Protein content was highest in fish fed with the CTRL diet, whereas the highest lipid content was observed in fish fed with U20 diet. The results show that the incorporation of IMTA-produced Ulva meal in Nile tilapia diets is possible up to 10 % without compromising growth performance, protein utilization, and protein retention of juveniles. The high capacity of Nile tilapia to digest all experimental diets suggests that Ulva meal is a practical partial replacement for fish meal in Nile tilapia diets.