人参茎叶提取物对刺参生长、免疫及抗病力的影响

以初始体重为(4.910.17) g的刺参(Apostichopus japonicas)为研究对象,研究投喂不同剂量人参茎叶提取物对刺参生长、免疫及抗病力的影响,探讨人参茎叶提取物在刺参养殖中的应用。在每千克基础饲料中分别添加10、20、40和80 g人参茎叶提取物作为实验组,并以基础饲料为对照进行为期30d的饲喂养殖。结果显示,投喂人参茎叶提取物对刺参的生长并无显著影响,刺参特定生长率不随人参茎叶提取物添加量的增加而提高。当人参茎叶提取物添加量为80 g/kg时,刺参体腔细胞总数、呼吸暴发强度、细胞吞噬活性、超氧化物歧化酶活力、总一氧化氮合酶活力均显著高于对照组(P0.05);当人参茎叶提取物添加量为40 g/kg时,细胞吞噬活性也显著高于对照组(P0.05),但其余免疫指标与对照组相比无显著差异(P0.05);当人参茎叶提取物的添加量不大于20 g/kg时,各项免疫指标与对照组之间均无显著差异(P0.05)。攻毒实验表明, 20、40和80 g/kg人参茎叶提取物组的健康率要高于对照组,其中80 g/kg人参茎叶提取物组健康率为80.56%要显著高于对照组和10 g/kg人参茎叶提取物组(P0.05)。人参茎叶提取物可作为免疫增强剂应用于刺参的养殖中来提高刺参的免疫和抗病能力。       

饲料中添加白术提取物对日本沼虾生长、健康和抗病力的影响

文章研究了饲料中添加不同水平的白术提取物(Extraction of Atractylodes macrocephala Koidz, EAMK)对日本沼虾(Macrobrachium nipponense)生产性能、器官指数、血液生化指标、抗氧化能力、消化系统健康和抗病力的影响。实验以初始体重为(0.21±0.05) g的日本沼虾为研究对象,设置6个饲料处理,白术提取物添加量为0、100、200、400、600和1200 mg/kg(Control、A100、A200、A400、A600和A1200)。每个饲料处理设6个重复,每个养殖缸放入60尾虾,实验周期为75d,每天记录采食量。养殖实验期间监测水体温度为(20±3)℃, pH为7.8—8.2,亚硝酸盐为0.16—0.2 mg/L,氨氮为0.02—0.1 mg/L,溶氧>6.0 mg/L。在实验结束后,分析日本沼虾生长性能、血清生化指标、肠道消化酶和免疫指标及肝胰腺抗氧化能力,观察日本沼虾的组织结构,用嗜水气单胞菌(Aeromonas hydrophila)进行攻毒并记录存活率。结果表明:饲料中添加200 mg/kg的白术提...     

饲料中添加叶酸和VB12对中华绒螯蟹幼蟹生长、非特异性免疫和抗病力的影响

为研究叶酸和VB12协同作用对中华绒螯蟹(Eriocheir sinensis)幼蟹生长、非特异性免疫和抗病力的影响,选取初始体重为(2.570.03) g的幼蟹600只,随机分成4组,每组5个重复,每个重复30只幼蟹,分别投喂对照组(不添加叶酸和VB12),单一VB12组(0.2 mg/kg),单一叶酸组(2.3 mg/kg)和联合处理组(0.2 mg/kg VB12 +2.3 mg/kg叶酸)的饲料8周。在养殖实验结束后,先统计成活率和称重,然后从每个处理组随机选取30只幼蟹,用2108 CFU/mL的嗜水气单胞菌注射攻毒2周。实验结果表明:幼蟹的增重率、特定生长率、饲料效率和存活率在联合处理组最高,显著高于对照组(P0.05),但与单一叶酸或VB12组相比不存在显著差异(P0.05)。联合处理组的血清酚氧化酶活性显著高于对照组(P0.05),但与单一叶酸或VB12组也无显著性差异(P0.05)。同时,联合处理组的血清酸性磷酸酶、碱性磷酸酶、溶菌酶活性和血细胞总数等指标最高,其次是单一叶酸组和VB12组,而对照组最低。投喂联合处理组饲料幼蟹的肝胰腺超氧化物歧化酶活性最高,而丙二醛含量和累积死亡率最低。以上结果表明,叶酸和VB12对幼蟹的生长、生理代谢和免疫性能均可能有互补和协同作用,养殖生产中建议饲料中叶酸和VB12添加量分别为2.3 mg/kg和0.2 mg/kg。       

VE对草鱼成鱼肌肉品质和抗氧化性能的影响

在VE含量为24.1 mg/kg的实用基础饲料中分别添加VE 0(对照组)、25、50、100、200 mg/kg,饲喂平均体重为(614.9±60.5)g的草鱼60d.考察VE对草鱼成鱼生长性能、肌肉品质和抗氧化性能的影响.结果表明,各组草鱼增重率分别为51.6%、53.5%、53.4%、53.5%、54.8%,饲料系数分别为2.28、2.17、2.20、2.19、2.15,饲料中添加25-200 mg/kg VE对草鱼成伍增重率、饲料系数无显著影响(P>0.05);在肌肉品质方面,饲料中添加VE对肌肉水分、粗蛋白、粗脂肪含量无显著影响(P>0.05).肌肉保鲜肉滴水损失和冷冻肉渗出损失随VE添加量的增加而降低;随饲料中VE添加量的增加,肌肉、肝脏中VE含量增加,丙二醛含量则显著降低(P<0.05),其中VE添加量为200 mr,/kg组的肌肉、肝脏VE含量较对照组增加431.0%、353.7%,丙二醛含量则下降67.2%、61.3%(P<0.01);在血清抗氧化能力方面,当VE添加量≥50 mg/kg后,草鱼血清SOD活性显著提高(P<0.05),而血清总抗氧化能力在VE添加量0-100 mg/kg各组间尤显著差异,200 mg/kgVE组的血清总抗氧化能力较对照组显著增高(P<0.05).上述研究表明,饲料中添加VE能促进草鱼生长,改善肌肉品质,增强机体抗氧化能力.以生长性能为标准,草鱼成鱼饲料(基础饲料含VE 24.1 mg/kg)中的VE添加量25 mg/kg;以肌肉品质、抗氧化能力指标为标准,草鱼成鱼饲料中的VE添加量为200 mg/kg.     

饲料中添加椭圆栅藻对异育银鲫中科5号越冬后抗病力的影响

为探究饲料中添加椭圆栅藻(Scenedesmus ovalternus)是否可以提高越冬期异育银鲫中科5号(Carassius gibelio var. CASⅤ)的免疫力和抗病力, 实验在异育银鲫中科5号[初重(109.24±0.23) g]越冬前期(4周)投喂基础饲料或者添加4%椭圆栅藻的饲料, 并在越冬结束后用嗜水气单胞菌(Aeromonas hydrophila)进行攻毒实验, 测定其生长、免疫力和抗病力等指标。结果表明在饲料中添加4%椭圆栅藻对中科5号的生长和攻毒后累计存活率无显著性影响(P>0.05)。髓过氧化物酶(MPO)活力在不同饲料处理中无显著性差异, 但是栅藻组在攻毒后MPO活力显著升高(P<0.05)。在嗜水气单胞菌攻毒后, 中科5号头肾中髓样分化因子88(MyD88)基因表达显著升高, 且栅藻组高于对照组(P<0.05)。此外, 摄食栅藻饲料的中科5号的Toll样受体4(TLR4)、包含Toll/白介素1的接头蛋白(TIRAP)和包含TIR结构域的IFN诱导连接蛋白(TRIF)基因表达也显著升高(P<0.05), 而对照组中无显著性变化(P>0.05)。因此, 中科5号摄食栅藻后MyD88依赖性或者MyD88非依赖性介导TLR信号通路可能都被激活以抵御病菌的入侵。综上所述, 在饲料中添加4%栅藻可以在一定程度上提高越冬后中科5号的抗病力, 可能是通过TLR通路进行调控。     

棉子糖对花鲈生长、免疫抗应激及抵御嗜水气单胞菌攻毒的影响

实验研究了棉子糖对花鲈(Lateolabrax japonicus)生长、非特异性免疫、抗应激能力和嗜水气单胞菌攻毒后存活率的影响。基础饲料依据花鲈营养需求配制。实验设计5个处理,棉子糖添加量分别为:0(对照组)、200、400、800和2000 mg/kg饲料,分别命名为R0、R200、R400、R800和R2000。每个处理3个重复,每个重复30尾鱼(初始体重3 g左右)。实验共持续16周,实验结束后称重并取血清样品用于测定免疫和抗氧化指标。此外还分别进行了30s空气暴露应激和嗜水气单胞菌攻毒实验。结果表明各实验组花鲈存活率和摄食率没有显著差异(P>0.05),R800组增重率显著高于对照组、R400和R2000组(P<0.05)。R400组饲料系数显著高于R800组、蛋白质效率显著低于R800组(P<0.05),但与其他各组没有显著差异。各组间蛋白质沉积率、肝指数没有显著差异(P>0.05),对照组、R200和R2000肥满度显著高于R400和R800组(P<0.05),R800组花鲈内脏比显著低于R400组(P<0.05)。各组间血清溶菌酶、超氧化物歧化酶活力和氧化产物丙二醛含量没有差异(P>0.05)。30s空气暴露应激后血清葡萄糖和皮质醇也未显示差异,但嗜水气单胞菌(Aeromonas hydrophila)攻毒后对照组累计存活率为65%,显著低于各试验组(P<0.05)。棉子糖在花鲈饲料里适宜添加量为800 mg/kg。     

饲料中添加胆汁酸对牛蛙生长性能、体组成和营养物质表观消化率的影响

试验研究了饲料中添加胆汁酸对牛蛙Rana (Lithobates) catesbeiana生长性能、体成分和营养物质表观消化率的影响。基础饲料以鱼粉、豆粕为主要蛋白源, 棕榈油为主要脂肪源, 在基础饲料中分别添加0、100、200和300 mg/kg的胆汁酸(含量99.1%)制作4种等氮等能的试验饲料。试验将144只牛蛙初始体重(75.014.23) g随机分为4组, 每组3个重复, 每个重复12只牛蛙, 进行为期8周的生长试验。结果显示: 各试验组牛蛙成活率和摄食率差异不显著(P0.05)。200 mg/kg胆汁酸添加组牛蛙的增重率、特定生长率、饲料效率、蛋白质效率和氮保留率显著高于对照组(P0.05)。在饲料中添加胆汁酸显著降低了牛蛙脏体指数和全体的脂肪含量(P0.05), 但不影响肌肉粗脂肪以及全体和肌肉水分、粗蛋白、粗灰分含量(P0.05)。各处理组间血清总胆固醇、甘油三酯、高密度脂蛋白胆固醇和低密度脂蛋白胆固醇浓度均无显著变化(P0.05), 血清尿素氮含量随着饲料中胆汁酸添加量的增加而降低, 添加300 mg/kg胆汁酸组牛蛙血清尿素氮含量显著低于对照组(P0.05)。血糖水平则随着胆汁酸添加量的增加而先降低后升高, 其中100 mg/kg胆汁酸添加组牛蛙血糖水平最低(P0.05)。100 mg/kg胆汁酸添加组牛蛙肠道脂肪酶活力显著高于对照组和300 mg/kg胆汁酸添加组(P0.05), 与200 mg/kg胆汁酸添加组之间差异不显著(P0.05), 蛋白酶活力与脂肪酶活力有相似的变化趋势, 而淀粉酶活力未受胆汁酸添加水平影响。各处理组饲料营养物质的表观消化率随饲料中胆汁酸添加量的增加而先升高后降低, 其中饲料添加200 mg/kg胆汁酸显著增加了牛蛙对饲料营养物质的表观消化率(P0.05)。结果表明: 在饲料中添加适量的胆汁酸能提高牛蛙对饲料的消化率, 提高饲料效率, 从而促进牛蛙的生长, 同时可促进蛙体脂肪代谢, 降低机体脂肪沉积, 提高牛蛙可食部分比例。根据本试验结果, 建议牛蛙饲料中胆汁酸添加水平为200 mg/kg。       

五步蛇毒对小鼠免疫功能的影响

目的 探索五步蛇毒对正常小鼠免疫功能的影响.方法 将KM小鼠随机分为5组,分别为空白组、五步蛇毒安全范围内低剂量组(30 mg/kg)、五步蛇毒安全范围内中剂量组(60 mg/kg)、五步蛇毒安全范围内高剂量组(120 mg/kg)(以下简称五步蛇毒低、中、高剂量组)以及西洋参组(30 mg/kg),每组10只.各组小...     

黄颡鱼饲料中添加谷胱甘肽降低藻毒素毒性作用的研究

通过60d的生长实验研究饲料中不同含量的谷胱甘肽(GSH)对黄颡鱼(Pelteobagrus fulvidraco Richardson)摄食含蓝藻粉饲料后的毒性保护作用。共配制6种近似等氮等能(粗蛋白45%,总能19.5kJ/g)的实验饲料。以不添加蓝藻粉、不添加GSH的饲料组作为正对照,其他5种饲料均添加7.5%的藻粉,微囊藻毒素(Microc ystins,MCs)含量约为58μg/g,GSH添加量分别为:0(负对照)、200、500、800和1400mg/kg。实验结果表明,第1至第30天时,负对照组与正对照组实验鱼的摄食率无显著性差异(P>0.05)。第31至第60天时,负对照组实验鱼的摄食率显著高于正对照和其他GSH添加组(P0.05),但各GSH添加组肾脏中GSH显著低于正对照而高于负对照(P<0.05)。200、500和800mg/kg GSH添加组肝脏和肌肉中丙二醛(MDA)含量显著低于负对照(P<0.05)。在整个实验期间,随着饲料中GSH含量的增加,肝脏、肾脏、全肠和肌肉中微囊藻毒素含量先显著下降,当GSH添加量为500和800mg/kg时达到稳定,直至GSH添加量为1400mg/kg时显著上升。根据对黄颡鱼增重,肝脏和肌肉中MDA的含量以及组织中毒素的分析,在饲料中添加500-800mg/kg GSH可以有效缓解黄颡鱼饲料中微囊藻毒素的毒性。       

紫苏子提取物对异育银鲫存活、生长以及体生化组成的影响

以初始体重(5.73±0.36)g的异育银鲫(Carassius auratus gibelio)幼鱼为实验对象,在室内水族箱中进行为期8周的摄食生长实验.以基础饲料为对照,分别添加紫苏子提取物100、300、500和800 mg/kg 配制实验颗粒饲料,研究饲料中不同剂量紫苏子提取物(Extractives of Perilla seeds,EPS)对异育银鲫生长、存活和体生化组成的影响.结果显示:基础饲料中添加300 mg/kg的紫苏子提取物的实验C组对异育银鲫有显著的促生长作用.该组(C组)异育银鲫不仅增重率最大(99.5%)、饲料效率和蛋白质效率最高(分别为42.74%和118.72%),而且脏体比最小;添加EPS各实验组与对照组异育银鲫躯体的水分(76%左右)、粗蛋白(16%-17%)和粗脂肪(4%-5%)含量没有显著影响.不过C组与其他各组相比,脂肪含量最低(4.11%), 低于对照组;而其蛋白含量最高(17.03%),高于对照组(16.45%);此外C组的内脏脂肪含量(5.23%)最低,显著低于对照组(9.21%).添加紫苏子提取物能相应提高躯体和内脏的PUFA和HUFA的含量,综合效果以C组添加300mg/kg紫苏子提取物的效果最好.实验表明,在饲料中添加300mg/kg的紫苏子提取物能显著提高异育银鲫的生长和食物利用率.     

Effects of potential probiotic Bacillus subtilis T13 on growth, immunity and disease resistance against Vibrio splendidus infection in juvenile sea cucumber Apostichopus japonicus

A feeding experiment was conducted to determine influences of potential probiotic Bacillus subtilis T13 (isolated from intestine of healthy sea cucumbers) on growth, immunity and disease resistance against Vibrio splendidus infection in juvenile sea cucumbers Apostichopus japonicus. Animals were fed with diets containing B. subtilis T13 at 0, 10(5), 10(7) and 10(9) CFU/g for 30 days, respectively. At the end of the growth trial, fifteen sea cucumbers from each aquarium were sampled for immune indices measurement. Then twenty sea cucumbers from each replicate were challenged with V. splendidus. Results showed that administration of B. subtilis T13 had significant effect on the specific growth rates (SGR) of sea cucumbers (P < 0.05). Phagocytosis, respiratory burst activity and total nitric oxide synthase (T-NOS) activity were significantly improved in coelomocytes of sea cucumbers fed with T13 at 10(9) CFU/g diet (P < 0.05). The highest values of the total coelomocytes counts (TCC) and superoxide dismutase (SOD) activity were found in sea cucumbers fed diet containing T13 at 10(9) CFU/g. The cumulative mortality after V. splendidus challenge decreased significantly in sea cucumbers fed with T13 at dose of 10(9) CFU/g (P < 0.05). The present study confirmed the potential beneficial effects of B. subtilis T13 as dietary probiotic in juvenile A. japonicus.     

Effects of dietary live yeast Hanseniaspora opuntiae C21 on the immune and disease resistance against Vibrio splendidus infection in juvenile sea cucumber Apostichopus japonicus

A feeding experiment was conducted to determine effects of Hanseniaspora opuntiae C21 on immune response and disease resistance against Vibrio splendidus infection in juvenile sea cucumbers Apostichopus japonicus. Sea cucumbers were fed with either diets containing C21 at 10⁴, 10⁵ and 10⁶ CFU g^?1 feed or a control diet for 30–50 days, respectively. After feeding for 30 days and 45 days, five sea cucumbers from each tank were sampled for immunological analyses. Results indicated that C21 significantly improved the phagocytic activity in coelomocytes of sea cucumbers (P < 0.05). Moreover, C21 administration significantly enhanced lysozyme (LSZ), phenoloxidase activity (PO), total nitric oxide synthase (T-NOS), superoxide dismutase (SOD), alkaline phosphatase (AKP) and acid phosphatase (ACP) activities in coelomic fluid, and LSZ, T-NOS, AKP and ACP activities in coelomocytes lysate supernatant (CLS) of sea cucumbers (P < 0.05). After feeding for 45 days, 10 sea cucumbers from each dose group were challenged with V. splendidus NB13. Cumulative incidence and mortality of sea cucumbers fed with C21 were found to be lower than those of control group. After feeding for 50 days, sea cucumbers in 10⁴ CFU g^?1 C21 treatment and control tanks were subjected to acute salinity changes (from 30 to 20) for 24 h in the laboratory, and the immunological parameters were measured to evaluate the immune capacities of the A. japonicus. Phagocytic, LAZ and T-NOS activities of C21-treated group were higher than those of control group, indicating that salinity stress tolerance of sea cucumber was enhanced by C21. The present results showed that a diet supplemented with C21 could stimulate the immune system of juvenile A. japonicus thus enhancing their resistance against V. splendidus.     

Effects of dietary β-glucan, mannan oligosaccharide and their combinations on growth performance, immunity and resistance against Vibrio splendidus of sea cucumber, Apostichopus japonicus

A 4-week feeding trial was conducted to investigate the effects of dietary β-glucan, mannan oligosaccharide (MOS) and their combinations on growth performance, immunity and disease resistance of sea cucumber Apostichopus japonicus. Sea cucumbers (1215 individuals with initial weight of 3.8?±?0.2?g) were fed nine practical diets according to a 3?×?3 factorial design: the basal diet as the control supplemented with three levels of β-glucan (0, 0.075, 0.15%?w/w), crossed with 0, 0.1% (w/w) or 0.2% (w/w) MOS. Immune indices including total coelomocytes count (TCC), phagocytosis, superoxide anion production, superoxide dismutase (SOD) activity and total nitric oxide synthase activity (T-NOS) were measured at days 7, 11, 15, 18, 22, 25 and 29. At the end of the feeding trial, all the sea cucumbers left were weighted to monitor growth, and then were challenged by Vibrio splendidus. The results showed that dietary β-glucan, MOS and their combinations significantly increased TCC, phagocytosis, superoxide anion production and SOD activity of sea cucumbers (P?相似文献   

Phytase can reduce theneedfor monocalcium phosphate supplementation in soybean and rapeseed meal‐based diets of black sea bream,Acanthopagrus schlegelii (Bleeker, 1854)

A feeding trial was conducted to study the effect of partial replacement of dietary monocalcium phosphate (MCP) with phytase on growth performance, feed utilization and phosphorus discharge in black sea bream, Acanthopagrus schlegelii. In the feeding trial, the control diet (designated as P1.5) was prepared with 1.5% MCP but without phytase, and the three other diets (designated as PP1.0, PP0.5 and PP0, respectively) were supplemented with 1.0%, 0.5% and 0% MCP, respectively, along with 200 mg (400 U) phytase/kg diet in each. Each diet was tested in triplicate tanks and fish were fed twice daily to satiation. After an 8‐week feeding trial in indoor flow‐through cylindrical fibreglass tanks (25 fish per tank, initial body weight: 11.5 ± 0.12 g), fish fed with PP1.0 and PP0.5 had no significant change in weight gain (WG), specific growth rate (SGR), protein efficiency rate (PER) or feed conversion ratio (FCR) compared to the control (p > .05), whereas fish fed with PP0 showed a significantly lower growth performance in the above parameters (p < .05). The addition of phytase did not affect the body composition or muscle composition. The apparent digestibility coefficients (ADCs) of crude protein and phosphorus increased when fish were fed diets in which MCP was replaced by phytase. Phosphorus discharge was also significantly reduced in fish fed diets in which MCP was replaced by phytase (10.2 ± 0.50 to 8.01 ± 0.47 g/kg weight gain). The present study suggests that dietary MCP can be reduced when phytase is added to the black sea bream diet, with a maximum MCP reduction level of up to 1% when phytase is supplemented at 200 mg (400 U)/kg diet. Thus, phytase in the diet of black sea bream is economically and ecologically beneficial.     

Phenotypic and genetic characterization of bacteria isolated from diseased cultured sea cucumber Apostichopus japonicus in northeastern China

During the winter-spring from 2004 to 2006 in northeastern China cultured Japanese sea cucumber Apostichopus japonicus suffered from a serious disease. Clinical signs included swollen mouth, skin ulceration and massive mortality. Clinical samples taken during this period were studied. Thirty-one bacterial samples were isolated from diseased sea cucumbers and identified through biochemical tests, 16S rRNA gene sequence analysis and PCR amplification, followed by pathogenicity determination. The results showed that the 31 isolates belonged to the genera Vibrio (64.5%), Shewanella (12.9%), Serratia (12.9%), Pseudoalteromonas (6.4%) and Flavobacterium (3.2 %). The 3 prominent strains were Vibrio splendidus (41.9%), Shewanella (12.9%) and Serratia odorifera biogroup I (12.9%). Pathogenicity tests demonstrated that 13 out of 31 isolates were pathogenic, including 8 strains of V splendidus, 3 strains of Shewanella sp. and 2 strains of Pseudoalteromonas tetraodonis. The pathogenic V splendidus showed the highest frequency of appearance. Median lethal dose (LD50) values (14 d) of V splendidus, Shewanella sp. and P. tetraodonis were 1.74 x 10(7), 7.76 x 10(6), 7.24 x 10(7) CFU g(-1) body weight of sea cucumber, respectively. The virulences differed by species: Shewanella sp. > V splendidus> P. tetraodonis. This is the first report of Shewanella sp. virulence in sea cucumber.     

Dietary administration of bovine lactoferrin influences the immune ability of the giant freshwater prawn Macrobrachium rosenbergii (de Man) and its resistance against Aeromonas hydrophila infection and nitrite stress

Haemocyte count, phenoloxidase activity, agglutinin levels, total protein content, bacterial clearance efficiency, resistance to the pathogen Aeromonas hydrophila and nitrite stress were measured in the giant freshwater inter-moult sub-adult prawn Macrobrachium rosenbergii (15-20 g) which had been fed diets containing bovine lactoferrin (Lf) at 50, 100, 200mg kg(-1) feed for 7 or 14 days. M. rosenbergii fed a diet containing 100mg Lf kg(-1) diet for 7 days showed significant (P<0.05) increase in total protein levels, agglutination titres against bacteria A. hydrophila and rabbit RBC, phenoloxidase activity, bacterial clearance (as observed through reduced number of circulating bacteria) as well as survival against A. hydrophila challenge. Increased bacterial clearance was also noticed in prawns fed Lf at 50 or 200mg kg(-1) for 14 days compared to control. Feeding of Lf at 50mg kg(-1) diet for 7 or 14 days was able to enhance only PO activity and reduce percent mortality against A. hydrophila challenge compared to its control. Total haemocyte count was higher in the lowest dose of Lf feeding, i.e. 50mg kg(-1) for 7 days. However, there was no significant alteration in the differential haemocyte population with respect to graded levels of Lf feeding for 7 or 14 days. A notable reduction in mortality percent after 120 h of nitrite stress was observed in prawn fed Lf at 100mg kg(-1) diet for 14 days. On the contrary, feeding of the highest dose of Lf, i.e. 200mg kg(-1) diet for 14 days failed to stimulate most of the innate immune parameters or reduce the percent mortality against A. hydrophila challenge or nitrite stress. It is therefore concluded that administration of Lf in the diet at 100mg kg(-1) for 7 days could enhance the immune ability of M. rosenbergii and increase its resistance to A. hydrophila infection or nitrite stress.     

High intakes of tin lower iron status in rats

The effects of relatively low (1, 10, and 50 mg/kg) and high (100 and 200 mg/kg) dietary concentrations of tin (added as stannous chloride) on iron status of rats were determined. After feeding the diets for 28 d, feed intake and body weights were not significantly affected. Iron concentrations in plasma, spleen, and tibia as well as percentage transferrin saturation were decreased in rats fed the diets supplemented with 100 or 200 mg tin/kg. In rats fed the diet containing 200 mg tin/kg, group mean hemoglobin, hematocrit, and red blood cell count were slightly lowered but total iron binding capacity was not affected. Iron status was not influenced by dietary tin concentrations lower than 100 mg/kg. If these results can be extrapolated to humans, then it may be concluded that tin concentrations in the human diet, which range from 2 to 76 mg/kg dry diet, do not influence iron status in humans.     

异育银鲫幼鱼对饲料中维生素K需求的研究

以不同维生素K水平(0.13、2.15、3.25、6.40、12、17.20和23.20 mg/kg饲料)的7种精制饲料喂养初始体重约为(2.17±0.01) g的异育银鲫(Carassius auratus gibelio)10周, 每个处理3个重复, 研究异育银鲫对维生素K的需求量。结果显示: 饲料中维生素K的添加可以明显降低摄食率, 饲料中维生素K含量为2.15 mg/kg时, 摄食率出现最大值, 之后显著下降(P<0.05), 在12 mg/kg时达到最低值。特定生长率随着维生素K的添加表现出升高的趋势, 饲料中维生素K含量为12 mg/kg时, 出现最大值, 但是差异不显著(P>0.05)。饲料中维生素K的含量从0.13 mg/kg升至3.25 mg/kg时, 饲料效率显著升高(P<0.05), 随着饲料中维生素K的进一步添加, 趋于稳定(P>0.05), 在12 mg/kg时达到最大值, 并且与特定生长率呈正相关关系(SGR=0.01 FE+0.95, R²=0.95)。血液红细胞数目随着饲料维生素K含量的增加先显著升高(P<0.05), 在6.40 mg/kg时达到最大值, 之后趋于稳定(P>0.05)。血红蛋白含量、血球容积比、血清钙含量与血液中红细胞数目表现出相似的趋势, 均在不添加维生素K组出现最低值, 但是差异不显著(P>0.05)。肝体比、肥满度及鱼体生化组成均不受饲料维生素K水平的影响(P>0.05)。分别对饲料效率、红细胞数目进行折线回归得出异育银鲫幼鱼对维生素K的最适需求量为3.73—6.72 mg/kg饲料。