喷雾干燥与冷冻干燥对鱼油微胶囊品质的影响

为深度开发金枪鱼加工副产物,充分利用金枪鱼油所含营养成分,以壳聚糖为壁材,金枪鱼油为芯材,分别采用喷雾干燥法和冷冻干燥法制备鱼油微胶囊,比较两种制备方法对制得微胶囊品质的影响。结果显示:喷干鱼油微胶囊和冻干鱼油微胶囊的包埋率分别为77.26%、63.86%,但后者对鱼油脂肪酸保护更好;前者挥发性成分共有43种,其中酮类物质相对含量最高,占33.01%;而后者的挥发性成分仅有24种,以酯类为主,占52.29%,且没有检测到典型的腥味物质,这可能是由于冻干过程温度较低,抑制了多不饱和脂肪酸的氧化,更能掩盖鱼油不良风味。贮藏试验显示,两种鱼油微胶囊与鱼油相比,过氧化值的增长速度均显著降低(P<0.05);贮存7d后,两种胶囊的二十二碳六烯酸(DHA)和二十碳五烯酸(EPA)保留率分别为82.22%和85.25%,两种制备方法对DHA和EPA保留率的影响不大(P>0.05)。研究表明,两种鱼油微胶囊制备方法对延缓鱼油氧化和掩蔽不良风味有一定作用,对制备鱼油微胶囊具有一定的参考意义。     

案例分析——美国西尼罗河热疫情的暴发与防控

自1999年美国报道首例人西尼罗河病毒(WNV)感染以来,已出现了41 000多例临床感染病例和1 700多例死亡病例。1999年至2012年间,美国因人感染WNV住院造成的花费累计约7.78亿美元。同时,马属动物的治疗和免疫接种及WNV的监控也给美国带来了更严重的经济负担。针对WNV感染,美国采取了一系列防控措施,如建立国家虫媒病毒监测系统(ArboNET)、控制流行地区蚊虫、开发新型诊断方法、实施疫苗免疫等。但是,由于美国至少有65种蚊子能够传播WNV,感染WNV的候鸟可长距离传播病毒,加之季节、气候、人类活动等因素,导致WNV在美国难以根除。本案例提示我国应注重完善国家外来人兽共患病监测系统和实验室诊断方法 ;加强公共卫生实验室能力建设;利用大数据,建立WNV长期预警模型;确定理想的哨兵动物;加强政府与企业的合作以及疫苗、驱蚊剂的研发;加强宣传,突出防控重点。     

Dietary vitamin E requirement of sub‐adult genetically improved farmed tilapia strain of Nile tilapia (Oreochromis niloticus) reared in freshwater

A two‐factor orthogonal test was conducted to determine the dietary vitamin E (VE, dl ‐α‐tocopheryl acetate) requirement for sub‐adult GIFT strain of Nile tilapia (Oreochromis niloticus) at two lipid levels, and evaluate its effect on antioxidant responses. A basal diet containing 60 or 130 g/kg of soybean oil was supplemented with 0, 20, 40, 60, 120 and 240 mg VE/kg, respectively. Each diet was fed to three replicate groups of tilapia with initial weight (80.3 ± 0.7) g for 10 weeks. Results showed that the weight gain, feed efficiency and hepatic VE retention of fish were significantly increased by the increased VE in diets. In groups with 60 and 130 g/kg lipid, fish fed diets supplemented with VE had higher serum superoxide dismutase (SOD) and catalase activity, and lower malondialdehyde content than fish fed the VE un‐supplemented diet (p < .05). The proximate composition of fish had no significant difference in the group with 130 g/kg lipid, whereas crude lipid and ash content were significantly affected by dietary VE in the group with 60 g/kg lipid. Based on broken‐line regression analysis, dietary VE requirement to support the maximum weight gain and serum SOD were 43.2–45.8 and 66.0–76.1 mg/kg in diets with 60 and 130 g/kg lipid, respectively.     

基于转录组测序技术挖掘长吻鮠生长关键基因

为挖掘我国名优鱼类长吻鮠 (Leiocassis longirostris)生长相关基因,本研究运用Illumina高通量测序技术比较分析了快速生长组[平均体质量为(534.02±53.68) g]和缓慢生长组[平均体质量为(108.41±4.96) g]各9尾长吻鮠的脑组织基因表达谱。测序共获得267 404 674个高质量测序片段(clean reads),通过2种不同生长速率长吻鮠脑组织转录组比较筛选出518个差异表达基因,其中,412 个基因表达量上调,106个基因表达量下调。对12个差异表达基因进行实时荧光定量PCR验证的结果与转录组测序结果一致。GO功能分类显示,大量差异表达基因富集到生长(growth)、生长因子活性(growth factor activity)和激素介导的信号通路(hormone-mediated signaling pathway) GO条目中。KEGG富集分析显示,一些差异表达基因在MAPK信号通路(MAPK signaling pathway)、转化生长因子β信号通路(TGF-beta signaling pathway)、钙离子信号通路(calcium signaling pathway)和神经活性配体–受体相互作用(neuroactive ligand-receptor interaction)等途径中富集。根据GO功能注释和KEGG富集分析,筛选出gnrh、thr、egr1、fgf18、sst、gipr、cart和crf等基因是调控长吻鮠生长发育的关键候选基因。本研究结果为后续深入研究长吻鮠生长调控机制提供了重要的参考资料。     

叶尔羌高原鳅低温下耗氧率和窒息点的研究

试验采用流水呼吸室法和静水呼吸室法测定了叶尔羌高原鳅在低温6.5~7.5℃条件下的耗氧率和窒息点。结果表明,叶尔羌高原鳅耗氧率具有昼夜节律性,耗氧高峰在5:00左右,低谷在15:00左右,其耗氧率和窒息点随体重的增加而增加,随水温的升高而增大。叶尔羌高原鳅适应低温能力较强,适宜生长温度6~29℃,最佳生长温度8~15℃。     

鸭病毒性肝炎鸭胚灭活疫苗的研究

以鸭病毒性肝炎病毒Ⅰ型ATCC毒株接种健康鸭胚,收集致死的全胚组织作制苗材料,用福尔马林灭活,以麸氨酸钠终止其作用。先后试制疫苗11批,在试验室免疫雏鸭71只,经强毒攻击后,总的保护率为90.4％。本疫苗免疫雏鸭3天后可产生较坚强的免疫力,在室温至少可保存11天,在4℃可保存254天。经在江苏、安徽、广东等省推广应用200000头剂,均安全有效,颇受用户欢迎,对控制鸭病毒性肝炎的流行起了重要作用。     

Effects of chromium yeast,tributyrin and bile acid on growth performance,digestion and metabolism of Channa argus

A 60‐day feeding trial was carried out to evaluate the effects of chromium yeast (CY), tributyrin (TB) and bile acid (BA) on the snakehead (Channa argus). The control (CT) group was fed the basal diet, and the experimental groups were fed 200 mg/kg CY (concentration: 1,000 mg/kg), 2.5 g/kg TB (purity: 45%) or 1 g/kg BA (purity: 30%) in addition to the basal diet. The addition of CY, TB and BA statistically increased the weight gain rate, and specific growth rate, whereas the feeding rate and feed conversion ratio were significantly reduced (p < 0.05). When compared with the CT group, TB elevated the serum glutathion peroxidase (GSH‐Px) activity; and BA reduced low density lipoprotein cholesterol (LDL‐C) contents significantly (p < 0.05). The three feed additives reduced intestinal malonaldehyde (MDA) levels dramatically. Tributyrin significantly enhanced intestinal trypsin and pepsin activities (p < 0.05). The activity of fructose‐1,6‐bisphosphatase and pyruvate carboxylase in the group fed CY was significantly lower than in the CT group. In conclusion, dietary inclusion of the three additives enhanced growth performance of C. argus. Dietary supplementation of CY affected protein, glucose and lipid metabolism. Diets with TB levels improved intestinal digestive enzyme activity and antioxidant capacity. The addition of BA improved glycolipid metabolism.     

Effects of water temperatures and dietary protein levels on growth,body composition and blood biochemistry of juvenile GIFT tilapia (Oreochromis niloticus)

This study was carried out to evaluate the effects of water temperature (WT) and dietary protein levels on growth, body composition and blood biochemistry of GIFT tilapia (Oreochromis niloticus; initial average body weight: 38.75 ± 0.61g, n = 20). The fish were fed with six diets contained graded levels of protein (209.6, 251.0, 302.4, 354.3, 401.9 and 456.8 g/kg) and raised in each of WT (22°C, 28°C and 34°C) for 8 weeks. Results showed that the growth, feed utilization and protein efficiency were significantly increased with the increase of dietary protein level and followed by the latter platform at each WT. The fish raised at 28 and 34°C showed similar growth performance, and their values were significantly higher than the fish raised at 22°C (p < 0.05). The lipid contents in whole body were decreases with the increase of dietary protein level at each WT. However, the whole‐body protein, ash and moisture contents were not affected by dietary protein level or WT (p > 0.05). The values of serum biochemical indices (ALP, ALT, AST and TCHO) were all decreased with the increase of dietary protein. The optimal dietary protein requirement for GIFT tilapia to achieve maximal growth performance is 374.4, 301.7 and 304.9 g protein/kg diet at 22, 28 and 34°C, respectively.     

莱州湾4种大型甲壳类的空间与营养生态位

根据2010—2019年夏季莱州湾底拖网调查数据,研究了4种大型甲壳类(中国明对虾、三疣梭子蟹、日本蟳和口虾蛄)的优势度、种间联结、空间生态位特征,并应用碳氮稳定同位素数据分析了4种大型甲壳类的营养级、营养生态位与摄食来源。结果显示,口虾蛄、日本蟳是目前莱州湾夏季甲壳类最主要的优势种,放流种类中国明对虾、三疣梭子蟹为群落的重要种;4种大型甲壳类的种间联结性不强,显著正联结主要出现于中国明对虾与其他三者之间;日本蟳空间生态位宽度最高(2.45),口虾蛄(2.13)次之,中国明对虾(1.92)和三疣梭子蟹(1.93)较低;生态位重叠较高主要发生于中国明对虾与其他3种之间;4种大型甲壳类营养级相近(3.02～3.28),中国明对虾生态位总面积最大,三疣梭子蟹与日本蟳、口虾蛄的生态位总面积相近,三疣梭子蟹和日本蟳的营养生态位重叠较高;摄食来源分析表明,中国明对虾摄食双壳类比例更高,其他3种摄食来源同质化程度较高。目前莱州湾三疣梭子蟹和中国明对虾的优势度低于口虾蛄和日本蟳,表明增殖放流虽然扩大了三疣梭子蟹和中国明对虾的种群规模,但尚未较大程度改变甲壳类群落结构。综合4种甲壳类的群落地位、种间联结性、空间生态位宽度与重叠、营养级与营养生态位以及摄食来源的研究结果,中国明对虾与其他三者竞争相对较小,而三疣梭子蟹与日本蟳、口虾蛄竞争较大。为最大程度发挥增殖效益,建议在确定放流地点和放流数量时,应着重考虑相近生态位物种对放流物种的竞争和限制。