氨氮对凡纳对虾免疫指标的影响

以凡纳对虾(Litopenaeus vannamei)为研究对象,研究氨氮对其免疫指标的影响。实验氨氮质量浓度梯度设置为0.05(对照)、0.5、1.0、1.5、2.0、2.5 mg／L,各氨氮梯度用4g／L的氯化铵溶液来调节。将暂养在自然海水(对照)中的凡纳对虾分别放入各实验梯度中,对虾体长为(8.5±0.5)cm。结果表明,氨氮对凡纳对虾血细胞数量、血清中的酚氧化酶活力、溶菌和抗菌活力的影响显著(F>F0.05),且随着氨氮质量浓度的升高,血细胞数量和溶菌、抗菌活力降低,酚氧化酶活力升高;在0-24 h实验时间内,各处理组(对照组除外)对虾血细胞数量和溶菌、抗菌活力呈下降趋势,酚氧化酶活力呈上升趋势,24 h后稳定在较低水平上。实验说明,随着氨氮水平升高,凡纳对虾免疫力明显下降,对病原菌的易感性提高,因此在养殖过程中,环境氨氮变化幅度不应超过0.5 mg／L,或长时间维持在较高氨氮水平(>0.5 mg／L)。     

Nutritional value of feed peas (Pisum sativum) in practical diet formulations for Litopenaeus vannamei

Dry peas of mixed Canadian prairie varieties which were commercially obtained and processed to provide a variety of meals were evaluated in practical shrimp feeds. Whole and de‐hulled peas were pin milled to produce raw flours. A portion of these meals were processed to produce whole extruded and de‐hulled extruded meals. Additionally, a portion of the whole pea meal was processed by infrared cooking to produce a micronized meal. The five meals were evaluated in practical diets for Litopenaeus vannamei under controlled laboratory conditions. The first experiment was designed to estimate apparent protein and energy availability of the various meals. Using a practical reference diet, the meals were substituted using a 70:30 ratio to produce the test diets. Based on contrasts, both extruding and micronizing the pea meals resulted in significant improvements in both apparent protein digestibility and apparent energy digestibility values. Apparent energy digestibility values for the various ingredients expressed as percentage ± SD were: whole raw, 72.3 ± 8.1; whole extruded, 86.0 ± 8.9; de‐hulled raw, 88.4 ± 4.4; de‐hulled extruded, 94.4 ± 10.0; whole micronized, 94.1 ± 10.2. To evaluate the response of shrimp to the diets containing pea meal, two 7‐week growth trials were conducted in the laboratory using a practical diet formulated to contain 360 g kg^?1 protein and 90 g kg^?1 lipid. In the first growth trial the shrimp had a mean initial weight of 0.66 g and six test diets were evaluated that included the basal diet and five diets for which the pea meals were included in the diet at 250 g kg^?1 dry weight replacing whole wheat. In the second growth trial the shrimp had a mean initial weight of 1.1 g and only the whole raw and whole extruded meals were evaluated at 50, 100 and 200 g kg^?1 inclusion in the diet. At the conclusion of the first growth trial weight gain ranged from 718 to 862% and at the conclusion of the second growth trial weight gain ranged from 394 to 502%, with no significant differences or discernible trends observed as a result of the various dietary treatments. Based on the observed results, the continued evaluation of feed peas as a potential ingredient of shrimp feeds is warranted. Additionally, if feed peas are suitably priced, commercial producers are encouraged to evaluate feed peas as an alternative protein and energy source.     

Preliminary evaluation of the seaweed Gracilaria cervicornis (Rhodophyta) as a partial substitute for the industrial feeds used in shrimp (Litopenaeus vannamei) farming

The aim of this study was to evaluate the use of Gracilaria cervicornis meal as a partial substitute for the industrial feeds used in shrimp (Litopenaeus vannamei) farming. A total of 90 L. vannamei juveniles (0.34 g) were assigned randomly into nine experimental units at a stocking density of 10 shrimp tank⁻¹ and fed a commercial shrimp feed (CSF; 35% crude protein) as a control treatment, a feed made entirely of G. cervicornis (GCM), and a mixture of equal parts of the commercial shrimp feed and the Gracilaria meal (MIX) for 30 days. Over the first 2 weeks of the experiment, the survival was high (100%) in all dietary treatments. However, at the termination of the feeding trial survival decreased to 40% in shrimp fed GCM, significantly lower (P<0.05) than survival of shrimp fed the commercial diet control (CSF) or MIX treatments (100%). The highest growth performance was obtained in the CSF or MIX treatment groups. The absolute growth increase in these groups was significantly higher than for shrimp fed GCM. Similarly, the specific growth rates (SGRs) of shrimp given feeds containing CSF (5.11% day⁻¹) and MIX (4.71% day⁻¹) were significantly greater (P<0.05) than that of shrimp fed GCM pellets (0.44% day⁻¹). The feed efficiency ratios (FERs) were 64 for CSF, 54.3 for MIX and 3.3 for GCM. The results obtained in this study indicated the effectiveness of using G. cervicornis as a partial substitute for shrimp feeds. To our knowledge, this is the first time that the concept that macroalgae can partially substitute for the industrial feeds used in shrimp (L. vannamei) farming has been demonstrated.     

冷藏温度下凡纳滨对虾组织黑变与内源多酚氧化酶活性相关性研究

[目的]探索凡纳滨对虾在冷藏过程中多酚氧化酶(PPO)活性变化程度与对虾黑变之间的相关性,明确关键控制点。[方法]通过感官鉴定、光电色差和分光光度测定凡纳滨对虾冷藏过程中的黑变规律,据此研究PPO活性变化与凡纳滨对虾黑变之间的相关性。[结果]试验表明,同一时间内凡纳滨对虾不同组织部位的PPO活性有明显差异,头部最高,腹部次之,最后是尾部。相关性分析表明,在冷藏过程中凡纳滨对虾黑变度与PPO活性变化均趋于上升,黑变度的变化规律与PPO的活性变化趋势呈显著正相关,头部、腹部、尾部的相关系数分别达到0.987 3、0.971 6、0.973 2,定量证明PPO活性变化是引起凡纳滨对虾黑变的主要因素。[结论]研究可为凡纳滨对虾冷藏期间的黑变控制提供理论依据。     

高密度CO2诱导制备虾糜凝胶的特性

为了探索高密度CO2诱导制备蛋白凝胶的可行性,以南美白对虾虾糜为材料,以常压热诱导凝胶为对照,研究压力5～30MPa、时间10～50min、温度50～70℃等因素对虾糜凝胶特性以及基本营养成分的影响。结果表明,高密度CO2处理能够使虾糜形成凝胶,压力、时间和温度对虾糜凝胶特性均有显著影响,在20MPa、60℃、30min和25MPa、60℃、30min条件下制备的虾糜凝胶品质相对较好;与热诱导凝胶相比,高密度CO2诱导的虾糜凝胶强度更大,同时也显著增加了虾糜凝胶的持水能力,减少了营养物质的流失。研究结果表明,高密度CO2具有促进凝胶形成和改善凝胶特性的作用,可以成为替代热处理成为蛋白凝胶制品生产的新技术。     

凡纳滨对虾瞬时耗氧速率和体长及溶氧水平的关系

研究了在水温为28℃，盐度为5．5的条件下，凡纳滨对虾瞬时耗氧速率和体长及溶解氧水平的关系。共测定了6种不同体长（1．36～10．84cm）凡纳滨对虾的瞬时耗氧速率。结果表明，凡纳滨对虾的瞬时耗氧速率V随时间的增加而降低，两者之间存有良好的线性相关，呼吸类型属于顺应型；V随水环境中溶解氧含量DO升高而增加，V与DO之间呈良好的线性相关；V随虾体长的增长而降低，两者之间也具有良好的线性关系。     

养殖南美白对虾对饲料中镉的富集规律研究

以南美白对虾为试验对象,分别研究对虾中可食部分与不可食部分对配给饲料中镉的富集规律及吸收动力学.结果表明:镉主要富集于对虾不可食部分,可食部分与不可食部分对镉的富集趋势基本一致,均随着镉质量分数的上升而增大,但不可食部分对镉的最高富集量明显高于可食部分.南美白对虾对饲料中镉的富集符合Logistic方程,回归方程决定系数都在0.97以上(p<0.05).方程拟合性好,可很好地描述南美白对虾养殖过程中对镉的富集规律.     

SPME-GC-MS在虾调味料风味检测中的应用

以南美白对虾虾头为原料,经过酶解和Maillard增香工艺,得到风味良好的虾风味料,采用顶空固相微萃取-气相色谱-质谱联用分析法(SPME-GC-MS)进行分析、鉴定它们特征的挥发性风味成分,探讨工艺条件对风味的影响,经NIST质谱数据库检索和文献对照,各检出57和63种成分,主要有烃类、醇类、醛类、酮类,和含氮化合物如吡嗪及含硫化合物等,它们的协同作用构成了虾风味料的特殊气味。将虾头酶解产物和Maillard增香型调味料的风味成分进行对照,比较发现吡嗪类化合物对于虾风味料的香气贡献最大,在两种风味料中分别检出了17和21种,归一化含量高达40.58%和47.83%。经Maillard反应处理后的风味料含有更多的醛类、呋喃类、吡嗪类和含硫化合物。结果表明,Maillard反应具有明显的增香作用,所制备的虾调味料具有更好的风味,该产物将既可以作为虾调味料使用,也可以作为复合调味品的基料,进一步扩展其应用范围。     

Immune responses of whiteleg shrimp,Litopenaeus vannamei (Boone, 1931), to bacterially expressed dsRNA specific to VP28 gene of white spot syndrome virus

In this study, dsRNA specific to VP28 gene of white spot syndrome virus (WSSV) of shrimp was synthesized in Escherichia coli in large scale and studied the immune response of shrimp to dsRNA‐VP28. The haematological parameters such as clotting time and total haemocytes counts, and immunological parameters such as prophenoloxidase (proPO), superoxide dismutase (SOD), superoxide anion (SOA) and malondialdehyde content, as well as the mRNA expression of ten immune‐related genes were examined to estimate the effect of dsRNA‐VP28 on the innate immunity of Litopenaeus vannamei. The activities of proPO, SOA and SOD significantly increased in haemocyte after dsRNA‐VP28 treatment, whereas MDA content did not change significantly. Among the ten immune‐related genes examined, only the mRNA expression of proPO, cMnSOD, haemocyanin, crustin, BGBP, lipopolysaccharides (LPs), lectin and lysozyme in haemocytes, gill and hepatopancreas of L. vannamei, was significantly upregulated at 12 h after dsRNA‐VP28 treatment, while no significant expression changes were observed in Toll receptor and tumour receptor genes. The increase of proPO and SOD activities, and SOA level and mRNA expression level of proPO, cMnSOD, haemocyanin, crustin, BGBP, LPs, lectin and lysozyme after dsRNA‐VP28 stimulation indicate that these immune‐related genes were involved in dsRNA‐VP28‐induced innate immunity in shrimp.     

碳酸盐碱度对南美白对虾幼虾的毒性作用

在水温21～22℃的野外条件下,采用单因子急性毒性实验法,研究水环境中碳酸盐碱度对淡化南美白对虾幼虾的毒性作用,为开展内陆碳酸盐型盐碱水域移殖、养殖对虾提供科学依据。结果表明,在pH为7 50～8 72、盐度为3 29～4 84的实验条件下,碳酸盐碱度对淡化南美白对虾幼虾毒性作用的24h半有效浓度(EC50)为2 60mmol L,其95%置信限为2 44～2 76mmol L;24,48,96h的半致死浓度(LC50)分别为14 29,12 55,12 01mmol L,95%置信限分别为13 82～14 78,11 58～13 55,8 19～14 32mmol L;安全浓度(SC)为2 90mmol L。未经淡化驯化的南美白对虾幼虾对内陆碳酸盐型盐碱水域环境是无法适应的。