酵母水解物对凡纳滨对虾生长、消化酶活性和肠道形态的影响

本实验旨在研究饲料中添加酵母水解物对凡纳滨对虾(Litopenaeus vannamei)生长性能、血清生化指标、肝胰腺消化酶活性以及肠道形态的影响。酵母水解物添加量分别为0%、1%、3%和5%,配制4种等氮等脂(42.5%粗蛋白和8.5%粗脂肪)的实验饲料。选取初始体重为(1.86±0.02)g的凡纳滨对虾480尾,随机分为4组,每组4个重复,每个重复30尾,进行为期8周的养殖实验。结果表明饲料中添加5%酵母水解物组的增重率(WGR)、特定生长率(SGR)和蛋白质效率(PER)显著高于对照组(P0.05),而该组饲料系数(FCR)最低(P0.05)。对虾全虾粗蛋白含量随饲料中酵母水解物的增加而呈上升趋势,且5%酵母水解物添加组显著高于对照组(P0.05)。添加5%的酵母水解物显著提高了凡纳滨对虾血清总蛋白(TP)和甘油三酯(TG)含量,降低了谷草转氨酶(AST)和谷丙转氨酶(ALT)的活性(P0.05)。各处理组肝胰腺淀粉酶活性和对照组相比差异不显著(P0.05),但3%酵母水解物添加组的胰蛋白酶和脂肪酶活性显著高于对照组(P0.05)。3%酵母水解物添加组的对虾肠道皱襞高度和皱襞宽度显著高于对照组(P0.05),而5%添加组的微绒毛高度显著高于对照组(P0.05)。综上所述,在本实验条件下,饲料中添加3%~5%的酵母水解物能有效改善凡纳滨对虾生长性能、提高饲料利用率、促进消化吸收以及改善肠道形态学指标。     

低鱼粉饲料中添加羟基蛋氨酸硒对凡纳滨对虾生长性能、抗氧化能力和抗亚硝酸盐胁迫的影响

[目的]本实验旨在研究低鱼粉饲料 中添加羟基蛋氨酸硒(HMSe)对凡纳滨对虾(Litopenaeus vannamei)生长性能、抗氧化能力及抗亚硝酸盐胁迫的影响。[方法]实验选用初始体质量为(0.90±0.05)g的凡纳滨对虾,分别投喂HMSe添加水平为0.000、0.375、0.750、1.500和2.250 mg/kg的实验饲料,命名为HMSe0 、HMSe1、HMSe2、HMSe3和HMSe4,每组3个重复,养殖8周。养殖实验结束后,进行12 h 的亚硝酸盐胁迫实验。[结果]结果表明,凡纳滨对虾的终末体质量(FBW)、增重率(WG R)和饲料效率(FE)随着饲料中HMSe水平的增加呈现先升高后下降的趋势,并在HMSe2组达到峰值。随着饲料中HMSe水平的提高,对虾全体和肌肉中的硒含量均显著增加,而全虾粗蛋白和粗脂肪的含量呈现先升高后降低的趋势,并分别在HMSe2组和HMSe1组达到最大值。HMSe4组中凡纳滨对虾的血清谷胱甘肽过氧化物酶(GSH-Px)和肝胰腺过氧化氢酶(CAT)活性显著高于HMSe0组。亚硝酸盐胁迫显著影响凡纳滨对虾的存活率。与胁迫前比较,胁迫后对虾肝胰腺中MDA含量升高,GST、CAT和T-SOD的活性降低,而补充适量的HMSe可减轻这些负面影响。根据凡纳滨对虾胁迫后成活率的二次多项式回归分析,低鱼粉饲料中凡纳滨对虾的HMSe最适添加量为1.350 mg/kg。[结论]综上所述,在低鱼粉饲料中添加0.750~1.350 mg/kg HMSe,能够提高凡纳滨对虾的生长性能、饲料利用率和抗亚硝酸盐胁迫的能力。     

5种锌源对凡纳滨对虾生长、生化和免疫指标的影响

在水温28~33℃、盐度27~31条件下,将体质量(0.340±0.001)g的凡纳滨对虾,随机分养到18个380L玻璃钢桶中,每桶放虾40尾,投喂在基础饲料中分别添加40mg/kg源于七水硫酸锌、蛋氨酸锌、甘氨酸锌、美多C-锌A型(结合型)和美多C-锌B型(包被型)锌的饲料(含锌量为78.28~86.18mg/kg),对照组不添加(含锌36.62mg/kg),喂养8周,每个处理3个重复。试验结果表明,锌添加组虾的质量增加率和特定生长率显著高于对照组(P0.05),其中蛋氨酸锌组最佳,饲料系数最低。锌添加组全虾粗脂肪和肝体比高于对照组,全虾粗蛋白及除美多C-锌B型组外的全虾粗灰分低于对照组(P0.05)。美多C-锌B型组凡纳滨对虾血清总蛋白含量最高,其次为蛋氨酸锌组;硫酸锌组虾血清甘油三酯和胆固醇均最高。蛋氨酸锌组虾血清总超氧化物歧化酶、碱性磷酸酯酶、酸性磷酸酶和酚氧化酶活性最高。锌添加组全虾锌含量显著高于对照组(P0.05),硫酸锌组虾肌肉锌含量显著高于对照组(P0.05),其他组与对照组和硫酸锌组无显著差异(P0.05)。综上所述,蛋氨酸锌促进凡纳滨对虾生长,提升免疫力的效果最佳,是饲料中适宜的锌源。     

聚β-羟基丁酸酯对凡纳滨对虾肝胰腺免疫和消化指标的影响

以平均体质量为(5.66±0.14)g的凡纳滨对虾(Litopenaeus vannamei)为研究对象,分别投喂含聚β-羟基丁酸酯(PHB)质量分数为0%(对照组)、1%、3%和5%的对虾配合饲料,饲养35 d后检测并比较不同水平PHB对凡纳滨对虾肝胰腺免疫和消化指标的影响。结果显示,3%PHB添加组凡纳滨对虾的总抗氧化能力和溶菌酶活性显著高于对照组(P0.05)。Toll基因表达量随PHB含量的升高呈先上升后下降趋势,其中1%和3%PHB添加组的表达量显著高于对照组(P0.05);对照组HSP70基因表达量显著低于其他处理组(P0.05)。5%PHB添加组的淀粉酶、胃蛋白酶和胰蛋白酶活性显著升高(P0.05),而脂肪酶活性无显著变化(P0.05)。由此可见,饲料中添加适量的PHB有利于增强凡纳滨对虾肝胰腺的消化和非特异性免疫能力。     

辣椒碱在凡纳滨对虾饲料中的应用研究

以凡纳滨对虾为试验对象,探讨在饲料中添加2 mg/kg的辣椒碱对凡纳滨对虾生长、免疫等方面的影响。试验结果表明,与对照组相比,试验组饲料中添加2 mg/kg辣椒碱后,凡纳滨对虾的生长性能指标显著改善,成活率、饲料系数显著优于对照组(P<0.05),血清中谷草转氨酶(AST)、谷丙转氨酶(ALT)含量显著高于对照组(P<0.05),肝胰腺免疫抗氧化指标(MDA、SOD、CAT)水平及健康状况亦有所提升。     

饲料中添加核苷酸对凡纳滨对虾幼虾生长、肠道形态及抗氧化酶活力的影响

本实验旨在研究外源核苷酸混合物对凡纳滨对虾(Litopenaeus vannamei)幼虾生长性能、体组成、中肠肠道形态和抗氧化酶活力的影响。选取960尾初始体质量为(1.01±0.02)g的凡纳滨对虾,随机分为8组,分别投喂基础饲料和添加5种核苷酸混合物(5′-腺苷酸∶5′-胞苷酸∶5′-尿苷酸二钠∶5′-肌苷酸二钠∶5′-鸟苷酸二钠=1∶1∶1∶1∶1,mix-NT)的实验饲料,各实验组添加量分别为0.1、0.2、0.4、0.6、0.8、1.0和1.2 g/kg饲料,养殖期为7周。结果显示,饲料中添加5种核苷酸混合物对凡纳滨对虾的特定生长率(SGR)和饲料系数(FCR)影响不显著(P>0.05)。外源核苷酸显著影响凡纳滨对虾全虾水分含量(P<0.05),但对全虾粗蛋白、粗脂肪和灰分含量影响不显著(P>0.05)。肝胰指数(HSI)随饲料中核苷酸添加量的增加而显著升高(P<0.05),在0.6 g/kg组达到最高。0.4 g/kg组的肝胰腺谷草转氨酶(GOT)和谷丙转氨酶(GPT)活力及尿酸(UA)含量最低,但与对照组相比差异均不显著(P>0.05)。中肠肠壁厚度和肠绒毛高度均随着核苷酸添加量的增加呈先升高...     

小球藻生长因子对凡纳滨对虾生长及营养成分的影响

为探明饲料添加小球藻生长因子对对虾生长性能、基础体成分和营养成分的影响,以凡纳滨对虾幼虾为试验对象,在基础饲料中分别添加0%、0.5%、1.0%、5.0%、10.0%、15.0%的小球藻生长因子,进行45 d的养殖试验,测定其生长性能、基础体成分和营养成分。试验结果显示,饲料添加小球藻生长因子能够提高凡纳滨对虾的存活率、质量增加率和特定生长率,降低饲料系数。饲料中添加小球藻生长因子能够降低凡纳滨对虾水分、粗脂肪和灰分含量,提高虾体粗蛋白含量,其中1%组凡纳滨对虾水分、粗脂肪、灰分均最低,粗蛋白最高。饲料添加10.0%～15.0%的小球藻生长因子凡纳滨对虾脂肪酸总量、饱和脂肪酸、单不饱和脂肪酸和多不饱和脂肪酸含量显著升高。饲料添加小球藻生长因子能够提高凡纳滨对虾多不饱和脂肪酸占比,降低饱和脂肪酸和单不饱和脂肪酸占比,其中1.0%组凡纳滨对虾饱和脂肪酸占比最低。饲料添加不同比例小球藻生长因子(除10.0%组)能显著提高肌肉氨基酸总量和必需氨基酸含量(P<0.05)。试验结果表明,饲料添加一定比例的小球藻生长因子能够提高凡纳滨对虾存活率和生长性能,降低水分、脂肪、灰分比例,提高蛋白比例...     

不同类型硒对黑鲷幼鱼生长及血清免疫指标的影响

在水温(27±1)℃下,将初始体质量为(13.00±0.20)g的黑鲷幼鱼放入容积为310L(水体260L)的微流水玻璃缸内,投喂含蛋白41.57%、脂肪13.63%等氮等能基础饲料(对照组)及在其中添加2.35mg/kg硒化多糖和0.88mg/kg的亚硒酸钠(使外源硒添加量均为0.4mg/kg)的试验饲料8周,研究了不同类型的外源硒对黑鲷幼鱼生长性能、体组成和血清免疫指标的影响。试验结果显示,黑鲷幼鱼摄食添加了硒化多糖和亚硒酸钠的饲料时,其特定生长率、血清免疫球蛋白M、补体C3、补体C4的含量以及肝脏和肌肉中硒的含量均显著高于对照组(P0.05),且添加硒化多糖组的上述指标显著高于添加亚硒酸钠组(P0.05);饲料中添加硒化多糖和亚硒酸钠对黑鲷幼鱼的形体指标和体组成无显著影响(P0.05)。试验结果表明,添加适量的外源硒能显著提高黑鲷幼鱼的生长性能和血清免疫活性,且有机硒的生物利用率显著高于无机硒。     

不同饲料能量源及其水平对凡纳滨对虾生长、抗氧化能力及蛋白质利用的影响

为探究不同饲料能量源及其水平对凡纳滨对虾(Litopenaeusvannamei)生长性能的影响,以饲料蛋白质含量为37%,蛋白能量比为20.23 mg/kJ的饲料作为对照组饲料(C),在此基础上分别通过提高饲料碳水化合物、脂肪含量调节饲料能量水平,制作饲料蛋白能量比分别为19.51 mg/kJ (中碳水化合物组, MC)、18.85 mg/kJ (高碳水化合物组, HC)、19.45 mg/kJ (中脂肪组, ML)和18.54 mg/kJ (高脂肪组, HL)的4组实验饲料,在淡水养殖条件下投喂初始体重为(0.6±0.02)g的凡纳滨对虾幼虾56d。结果表明,与对照组相比,提升饲料脂肪水平能显著提高凡纳滨对虾的生长性能和蛋白质沉积率(P<0.05),HL组凡纳滨对虾获得最大特定生长率及蛋白质沉积率;增加饲料碳水化合物水平对凡纳滨对虾的生长性能及蛋白质沉积率无显著影响(P>0.05)。与对照组相比, ML组、MC组、HC组对虾肌肉粗蛋白含量显著提高(P<0.05),HL组对虾肌肉粗蛋白含量较对照组有所提高,但差异不显著(P>0.05),对虾肌肉总脂肪含量则随着...     

酵母提取物替代鱼粉对凡纳滨对虾消化机能的影响

为探明使用经氨基酸平衡后的酵母提取物替代鱼粉对凡纳滨对虾消化机能的影响,分别用酵母提取物替代饲料中15 %(B)、30 %(C)、45 %(D)、60 %(E)和100 %(F)的鱼粉,配制6种等氮、等能的试验饲料投喂凡纳滨对虾(6.328±0.630 g),以鱼粉含量为25 %的饲料为对照组(A)。饲养7 d后开始收集粪便,测定凡纳滨对虾对饲料的表观消化率。养殖试验结束后,研究酵母提取物替代鱼粉对凡纳滨对虾消化酶的影响。试验结果:凡纳滨对虾对各组饲料均具有较高的干物质表观消化率(77.96 %~81.21 %)和粗蛋白表观消化率(87.19 %~92.82 %)；各替代组饲料的表观消化率均高于对照组,其中C、E和F组的干物质表观消化率显著高于对照组(P<0.05),粗蛋白表观消化率随酵母提取物用量的增加而显著增加(P<0.05)；凡纳滨对虾肝胰腺中类胰蛋白酶的活性随饲料中酵母提取物用量的增加而显著升高(P<0.05),脂肪酶的活性随饲料中酵母提取物用量的增加而显著降低(P<0.05)；肝胰腺中淀粉酶活性最高的为C组；各替代组凡纳滨对虾的肠胰蛋白酶活性均高于对照组。结果表明,以氨基酸平衡酵母提取物替代饲料中的鱼粉可以提高凡纳滨对虾对饲料的消化机能。     

仿刺参体壁硒含量衰减与硒化合物的关系

在水温13℃、盐度27、pH 8.1的条件下,将初始体质量为(54.97±9.49)g的仿刺参成参和(2.28±0.26)g的幼参饲养在水槽中,分别投喂在基础饲料中添加0.3mg/kg硒代蛋氨酸、硒酸钠、亚硒酸钠的试验饲料,以未添加硒的基础饲料作为对照组,每个试验组设3个重复。60d后,成参组继续投喂基础饲料60d,幼参组45d,中间每隔5d测定一次硒含量。试验结果表明,成参组中,体壁硒含量衰减速度依次为硒酸钠组亚硒酸钠组硒代蛋氨酸组;幼参组中,体壁硒含量衰减速度依次为亚硒酸钠组硒酸钠组硒代蛋氨酸组。研究表明,富硒成参生产过程中最佳硒添加剂为硒代蛋氨酸。     

Dietary choline improves growth performance,antioxidant ability and reduces lipid metabolites in practical diet for juvenile Pacific white shrimp,Litopenaeus vannamei

An 8‐week feeding trial was conducted to evaluate the effects of dietary choline levels on growth performance, antioxidant capacity and lipid metabolites in juvenile Pacific white shrimp. Six isonitrogenous and isolipidic diets were formulated to supply 0, 1,000, 2,000, 4,000, 6,000, 10,000 mg/kg choline chloride, and dietary choline levels were analysed to be 1,317 (basal diet), 1,721, 2,336, 3,294, 5,421 and 9,495 mg/kg, respectively. Dietary choline levels significantly influenced percent weight gain (PWG) and protein efficiency ratio (PER), with the highest PWG was observed in shrimp fed the 5,421 mg/kg choline diet. However, there were no significant differences in proximate composition of whole body and muscle. Shrimp fed the diet containing 2,336 mg/kg choline had lower HDL and LDL in haemolymph than those fed the basal diet (1,317 mg/kg diet). Dietary choline prevented the accumulation of free radicals and improved antioxidant capacity by increasing catalase activity and reducing malondialdehyde content. Based on broken‐line regression and quadratic regression analysis between PWG against dietary choline levels, the optimal choline requirements were estimated to be 3,254.1 and 6,488.3 mg/kg for juvenile L. vannamei, respectively.     

The effects of dietary organic or inorganic selenium in rainbow trout (Oncorhynchus mykiss) under crowding conditions

In the present study, the effects of different sources of selenium (Se; sodium selenite or selenomethionine) supplementation on the growth and serum concentrations of oxidative stress markers [malondialdehyde (MDA), 8‐isoprostane, glutathione peroxidase (GSH‐Px) activity] and muscle Se, MDA and heat shock protein 70 (Hsp70) levels in rainbow trouts were evaluated. The fish (n = 360; 0 + years old) with initial average weight of 20 ± 0.8 g were randomly assigned to 12 treatment groups consisting of 3 replicates of 10 fish each in a 2 × 2 × 3 factorial arrangement of treatments (stocking densities, Se sources, Se levels). The fish were kept at low (25 kg m^?3) or high (100 kg m^?3) stocking densities and fed a basal (control) diet or the basal diet supplemented with either 0.15 or 0.30 mg of Se kg^?1 of diet from two different forms: sodium selenite or selenomethionine. High stocking density decreased weight gain, feed intake and feed conversion ratio (FCR) when basal diet was fed (P = 0.001). A linear increase in feed intake and weight gain and improvement in FCR were found in sodium selenite (P = 0.01)‐ or selenomethionine (P = 0.001)‐supplemented fish reared under crowding conditions. Serum and muscle Se levels and serum GSH‐Px activity increased (P = 0.001) linearly, whereas serum and muscle MDA concentrations and serum 8‐isoprostane decreased linearly as dietary sodium selenite (P = 0.01) or selenomethionine (P = 0.001) supplementation increased. Selenomethionine and sodium selenite supplementation decreased Hsp70 in the muscle of fish reared under crowding conditions (P < 0.05). Supplementation with Se improved growth and antioxidant status of fish and the effects of selenomethionine were relatively greater than sodium selenite in the crowded groups. Results suggest that crowding conditions cause significant detrimental effects in rainbow trout indicated by increased oxidative stress, reduced feed intake and body weight gain. ?t also indicates that dietary Se supplementation offers a feasible way of reducing the losses in performance of rainbow trout reared under crowding conditions. Selenomethionine seems to be more effective than sodium selenite and the higer dose in the present study also seems to be more effective than the lower dose.     

Comparison of Purified and Practical Diets Supplemented with or without β-Glucan and Selenium on Resistance of Hybrid Striped Bass Morone chrysops ♀× M. saxatilis ♂ to Streptococcus iniae Infection

This study was conducted to evaluate the efficacy of β-glucan and selenium supplements to the diet on increasing survival of hybrid striped bass Morone chrysops X M. saxatilis exposed to Streptococcus iniae. A 2 × 2 × 2 factorial design was employed by including purified casein/gelatin-based diets and practical menhaden fish meal-based diets with supplement! of either β-glucan from barley at 0 and 0.1 % of diet or sodium selenite at 0 or 0.2 mg/kg diet or a combination of these supplements. All diets were formulated to meet the nutritional needs of hybrid striped bass with the exception of selenium. The purified and practical basal diets contained 0.03 and 1.03 mg Se/kg, respectively, and the diets supplemented with sodium selenite had an additional 0.07 mg Se/kg on average. Juvenile hybrid striped bass initially averaging 2.44 ± 0.17 g/fish were fed the eight experimental diets in triplicate 110-L recirculating aquaria for 6 wk, after which they were immersed in a bath of S. iniae at 6.2 × 10⁶ CFU/mL for 2 h and monitored for 21 d. Weighi gain and feed efficiency were significantly (P < 0.05) affected by diet type and selenium supplementation, with fish fed practical diets and those supplemented with selenium having the greatest values. Supplementation of β-glucan to the purified or practical type diets did not significantly affect survival of fish after experimental infection. The most notable difference (P < 0.0001) was in the comparison of diet type; the survival rate of fish fed the practical diets was 75% compared to 35% for those fed the purified diets. Dietary supplementation of β-glucan did not enhance disease resistance in the present study. Fish fed menhaden fish meal-based diets were significantly more resistant to 5. iniae in comparison to the those fed the purified diets. Thus, nutritional influences on disease resistance of hybrid striped bass were evident in this study and warrant further investigation.     

Effects of dietary selenium on growth performance and oxidative stress in juvenile grass carp Ctenopharyngodon idellus

An 8‐week feeding trial was conducted to investigate the effect of dietary selenium (Se) on feed intake, weight gain and antioxidant activity in juvenile grass carp (11.2 ± 0.03 g). Six Se levels (0.13, 0.41, 0.56, 1.12, 2.18 and 4.31 mg/kg) of semi‐purified diets were assayed in triplicate. The maximum weight gain, specific growth rate and feed intake were obtained in fish fed with 1.12 mg Se/kg diet. Hepatic glutathione peroxidase activity was markedly increased when dietary Se ≤1.12 mg/kg diet and reached a plateau when dietary Se ≥1.12 mg/kg diet. Hepatic superoxide dismutase and serum catalase activities in juvenile grass carp fed with 0.56, 1.12 and 2.18 mg Se/kg diets were all significantly higher than those in the other groups. The malondialdehyde content in liver and serum was firstly decreased and then increased with increasing dietary Se content, and the lowest content was observed in fish fed with 1.12 mg Se/kg diet. With the increase in Se level, the activities of serum alanine aminotransferase and aspartate aminotransferase were reduced. In addition, serum alkaline phosphatase activity and albumin content were highest in fish fed with 1.12 mg Se/kg diet. This study indicated that both the Se deficiency and excess of Se caused negative effect on the oxidative stress in juvenile grass carp and suggested that the health‐giving concentration of dietary inorganic Se was 1.12 mg/kg diet. Moreover, based on the broken‐line regression analysis of weight gain, the optimal concentration of dietary inorganic Se was 0.83 mg/kg for juvenile grass carp.     

Effects of dietary selenium on the growth,selenium status,antioxidant activities,muscle composition and meat quality of blunt snout bream,Megalobrama amblycephala

An 8‐week feeding trial was performed to investigate effects of dietary selenium (sodium selenite, Na₂SeO₃; selenium nanoparticle, Nano‐Se; selenium yeast, Se‐yeast) on the growth, selenium status, antioxidant activities, muscle composition and meat quality of blunt snout bream. Na₂SeO₃ and Nano‐Se were supplemented at 0.2 mg Se kg^?1, and Se‐yeast was supplemented at 0.1, 0.2, 0.4 and 0.8 mg Se kg^?1 in basal diet; no Se was added as a control. The results indicated that groups of 0.2 and 0.4 mg kg^?1 Se‐yeast had significantly higher weight gain and Nano‐Se, 0.2, 0.4 mg kg^?1 Se‐yeast had significantly lower feed conversation ratio compared with the control group. The Se concentrations of whole body, muscle and liver linearly increased with increasing dietary Se‐yeast levels. Group of 0.4 mg kg^?1 Se‐yeast significantly increased activities of catalase and glutathione peroxidase. Muscle colour of Nano‐Se, 0.2, 0.4 mg kg^?1 Se‐yeast groups, the water‐holding capacity of 0.4, 0.8 mg kg^?1 Se‐yeast groups showed significant differences compared with the control group. The results suggest that Se‐yeast and Nano‐Se had a better growth performance than Na₂SeO₃ at 0.2 mg Se kg^?1, and supplementing appropriate Se‐yeast in diet can increase antioxidant activities and enhance meat quality of blunt snout bream.     

Supra-nutritional dietary intake of selenite and selenium yeast in normal and stressed rainbow trout (Oncorhynchus mykiss): Implications on selenium status and health responses

Commercial salmonid diets are not typically supplemented with selenium (Se) as they naturally contain relatively high levels of this essential trace element; however supplementation may be necessary to meet requirements during physical stress. Adopting an integrated approach by simultaneously determining Se status, various health parameters and interactions with other trace elements, this study aimed to determine the role of supra-supplemented selenite and Se-yeast (Selplex^®) on the growth and health of rainbow trout (Oncorhynchus mykiss), both under normal conditions and after exposure to chronic physical stress. Fish were fed one of seven diets; a basal un-supplemented diet (0.73 mg kg^− 1 Se) or diets supplemented with Se-yeast or sodium selenite to provide 2, 4, or 8 mg kg^− 1 Se for 10 weeks prior to subjection of daily handling and confinement stressors for seven days. Net whole body Se retention was significantly greater for Se-yeast than selenite at all levels. In normal conditions activities of hepatic glutathione peroxidase (GSH-Px) and thioredoxin reductase (Trx-R) indicate that Se requirements were met by the basal diet. Similarly, pre-stress supra-supplementation of selenite and Se-yeast did not affect oxidative status (total antioxidant capacity of serum and hepatic malondialdehyde), immuno-competence (respiratory burst activity, serum lysozyme, and leukocyte counts) or other haematological and growth parameters (nuclear abnormalities in erythrocytes, and specific growth rate). In contrast, the trend towards a higher GSH-Px post-stress in Se supplemented diets over the basal diet, particularly in Se-yeast fed fish, indicates that Se requirements may not be met by the un-supplemented practical diet in stressed fish. Seven days of chronic physical stress decreased whole body Se and increased GSH-Px activity signifying an increased Se utilisation. During stress Se status was more effectively maintained by Se-yeast than selenite. Increased hepatic lipid peroxidation in stressed fish fed 8 mg kg^− 1 selenite indicates a possible pro-oxidant effect of selenite. A positive interaction was observed between dietary selenite and whole body copper, but no such interaction was observed with Se-yeast. This study concludes that physical stressors can result in an elevated Se utilisation and consequently supplementation of commercial diets may be necessary such that Se reserves are available as a contingency for stress.     

贯众、当归、黄芪对半滑舌鳎血液抗氧化指标的影响

在水温(21±1)℃和盐度20±1下,将体质量(95.45±5.29)g的半滑舌鳎饲养在78cm×58cm×46cm水槽中,投喂按0、5、10、15g/kg添加贯众、当归、黄芪的饲料,每箱20尾,每个水平3个重复,7d、14d和21d时尾柄采血,测定总超氧化物歧化酶和过氧化氢酶活性以及总抗氧化能力、丙二醛、总胆固醇和甘油三酯含量。试验结果表明,14d时,贯众剂量为15g/kg组的半滑舌鳎血液中总超氧化物岐化酶活力显著高于对照组(P0.05),14d和21d时,各剂量组丙二醛含量均低于对照组;14d时,当归剂量为5g/kg组的半滑舌鳎血液中总超氧化物岐化酶活力达到最高值;21d时,黄芪剂量为10g/kg组的丙二醛含量值显著低于对照组(P0.05),21d时,黄芪剂量为5g/kg组的半滑舌鳎血液中总超氧化物岐化酶活力达到最高值,不同剂量的黄芪对过氧化氢酶活力有显著影响,但均低于对照组(P0.05);7d时,各组总抗氧化能力达到最高值。试验表明,单独添加贯众、当归及黄芪均不同程度地影响半滑舌鳎血液的抗氧化指标。     

Dietary selenium requirement for juvenile cobia,Rachycentron canadum L.

A 10‐week feeding trial was conducted to estimate the optimum dietary selenium (Se) requirement for juvenile cobia, Rachycentron canadum L. The basal diet was formulated to contain 50.6% crude protein from vitamin‐free casein, gelatin. A control diet (no added seleno‐dl ‐methionine) and five experimental diets containing 0.20, 0.40, 0.60, 0.80 and 1.00 mg seleno‐dl ‐methionine kg^?1 were prepared. Each diet was randomly fed to triplicate groups of juvenile cobia with initial weight 6.27±0.03 g in a flow‐through system. The Se concentration in rearing water was monitored during the feeding period, and was not detectable. The dietary Se level significantly influenced the survival, specific growth rate (SGR), feed efficiency and the Se concentrations in the whole body and vertebra of cobia. The Se‐dependent glutathione peroxidase (EC 1.11.119) activity increased with an increase in the dietary Se levels (P<0.05). Hepatic glutathione reductase (EC 1.6.4.2) activity was the highest in fish fed the diet with 0.21 mg Se kg^?1, and declined with an increase in the dietary Se levels. Based on broke‐line regression of SGR, the Se concentration in the whole body and vertebra, the Se requirements of juvenile cobia were 0.788, 0.811 and 0.793 mg Se kg^?1 diet in the form of seleno‐dl ‐methionine respectively.