Dietary leucine requirement for juvenile large yellow croaker <Emphasis Type="Italic">Pseudosciaena crocea</Emphasis> (Richardson, 1846)

Dietary leucine requirement for juvenile large yellow croaker, Pseudosciaena crocea Richardson 1846 (initial body weight 6.0 g ± 0.1 g) was determined using dose-response method. Six isonitogenous (crude protein 43%) and isoenergetic (19 kJ g⁻¹) practical diets containing six levels of leucine (Diets 1–6) ranging from 1.23% to 4.80% (dry matter) were made at about 0.7% increment of leucine. Equal amino acid nitrogen was maintained by replacing leucine with glutamic acid. Triplicate groups of 60 individuals were fed to apparent satiation by hand twice daily (05:00 and 17:30). The water temperature was 26–32°C, salinity 26–30 and dissolved oxygen approximately 7 mg L⁻¹ during the experimental period. Final weight (FW) of large yellow croaker initially increased with increasing level of dietary leucine but then decreased at further higher level of leucine. The highest FW was obtained in fish fed diet with 3.30% Leucine (Diet 4). FW of fish fed the diet with 4.80% Leucine (Diet 6) was significantly lower than those fed Diet 4. However, no significant differences were observed between the other dietary treatments. Feed efficiency (FE) and whole body composition were independent of dietary leucine contents (P > 0.05). The results indicated that leucine was essential for growth of juvenile large yellow croaker. On the basis of FW, the optimum dietary leucine requirement for juvenile large yellow croaker was estimated to be 2.92% of dry matter (6.79% of dietary protein).     

Agroecological measures and circular economy strategies to ensure sufficient nitrogen for sustainable farming

Sustainable food systems face trade-offs between demands of low environmental pressures per unit area and requirements of increasing production. Organic farming has lower yields than conventional agriculture and requires the introduction of nitrogen (N) fixing legumes in crop rotations. Here we perform an integrated assessment of the feasibility of future food systems in terms of land and N availability and the potential for reducing greenhouse gas (GHG) emissions. Results show that switching to 100% organic farming without additional measures results in N deficiency. Dietary change towards a reduced share of animal products can aggravate N limitations, which can be overcome through the implementation of a combination of agroecological, circular economy and decarbonization strategies. These measures help to recycle and transfer N from grassland. A vegan diet from fully decarbonized conventional production performs similarly as the optimized organic scenario. Sustainable food systems hence require measures beyond the agricultural sector.     

植酸对牙鲆生长和消化酶活性的影响

以鱼粉为主要蛋白源,在基础饲料中分别添加不同含量的植酸纳使植酸水平分别达到0.04%(对照组)、0.21%、0.44%和0.81%,研究不同含量植酸对牙鲆(Paralichthys olivaceus)(2.58 g±0.01 g)摄食、生长和消化酶活性的影响.实验在室内循环水养殖系统中进行,为期10周.结果表明,植酸处理组牙鲆摄食率(2.4%、2.5%和2.4%)显著高于对照组(2.1%)(P＜0.05),但植酸处理组之间差异不显著(P＞0.05).植酸处理组(59.47、61.27和64.82 U/mg蛋白)胃蛋白酶比活力显著低于对照组(79.34 U/mg蛋白),但植酸处理组之间差异不显著.各处理组之间牙鲆肝脏、肠和胃中淀粉酶比活力及肝脏和肠中蛋白酶比活力均无显著差异.随着饲料中植酸含量的增加,干物质和蛋白质表观消化率显著下降.同时,牙鲆特定生长率、饲料转化率、蛋白质效率和净蛋白质利用率随着饲料中植酸含量的升高均呈下降趋势,其中各处理组之间牙鲆特定生长率无显著差异,而植酸处理组饲料转化率(74.0%、73.7%和69.2%)则显著低于对照组(84.0%),0.81%植酸处理组蛋白质效率(1.37)和净蛋白质利用率(25.0%)显著低于对照组(1.64和30.6%).本实验结果表明,随着饲料中植酸含量的增加,牙鲆生长性能和胃蛋白酶比活力呈下降趋势.植酸对牙鲆生长的抑制作用将随着其含量的升高或实验周期的延长突现出来.     

长蛸(Octopus minor)初孵幼体培育与生长研究

采用光滑河蓝蛤和菲律宾蛤仔两种双壳贝类培养长蛸幼体,分析其生长和存活情况。结果显示,长蛸初孵幼体无外卵黄,体表光滑,第一对腕(最长腕)约为胴长的2.9倍,腕吸盘两列,第1—4对腕平均吸盘数(n=3)分别为66±4.60、55±3.76、43±4.59和41±3.82;1—15d幼体投喂的是光滑河蓝蛤(壳长15.4—20.3mm),之后投喂菲律宾蛤仔(壳长33.2—39.3mm);幼体30d—70d总成活率由80.99%降至54.65%;整个培育过程中,幼体生长率与饵料效率呈极显著线性回归关系(P0.01),y=1.452x-2.731(R2=0.865);1—80d胴长/全长比增幅高于腕长/全长,表明胴体增长快于腕的增长;各腕吸盘数变化不显著;幼体鲜重与培养天数呈指数函数关系,Wt=0.301e0.010t(R2=0.854,P0.01);长蛸幼体最终生长率为122.05%,平均生长率为9.97%/10d。     

鱼蛋白酶水解物制备及其生物学评价

提出用枯草杆菌中性蛋白酶水解，从Ｅｎｇｒａｕｌｉｓｊｏｐｏｎｉｃｕｓ中提取鱼蛋白酶水解物。指出依次用活性炭和β－环糊精处理水解物可以去苦味，可溶性氮产率达８９．８０％。水解物氨基酸组成平衡，游离氨基酸占总氨基酸６２．７０％。并对水解物作出生物学评价。通过大鼠氮平衡试验和生长试验表明，水解物具有较高营养价值。可以认为，该鱼蛋白水解物可用作手术前后病人的要素饮食或要素饮食添加剂。     

虾池基础饵料及对虾养成期敌害生物的初步调查

作者于1983～1984年在普陀朱家尖和定海北蝉大成对虾养殖场调查时,发现虾池内基础饵料生物优势种有4种,主要敌害生物(鱼类)为23种。试验证明,用鱼藤精(1×10~(-6))杀灭敌害生物效果很好,而对对虾无不良影响。     

能量代谢研究对水产配合饲料研制和评价的应用价值

结合锯缘青蟹幼体能量代谢的研究成果，本文从能量转化效率、摄食代谢和特殊动力作用(SDA)、饲料的适宜能量浓度和能量蛋白比(C/P)及能量代谢的底物四个方面，阐述能量代谢的研究在水产配合饲料研制和评价方面的应用及其发展前景.     

不同饵料强化剂对龙虎斑仔稚鱼生长、存活率、消化酶活力及体成分的影响

褶皱臂尾轮虫(Brachionus plicatilis)与卤虫(Artemia franciscana)无节幼体分别以浓缩小球藻、深海鱼油和鱼肝油强化后,投喂龙虎斑(Epinephelus fuscoguttatus♀×E.lanceolatus♂)仔稚鱼,研究不同强化剂对仔稚鱼生长、存活率、消化酶活力及体成分的影响。结果显示,3种强化剂强化后的生物饵料均可显著提高龙虎斑仔稚鱼的存活率、体长和体质量,差异有统计学意义(P0.05),但对鱼体粗脂肪含量以及肠淀粉酶活力的影响无统计学意义(P0.05)。深海鱼油组仔稚鱼存活率最高,浓缩小球藻可以显著提高胃、肠蛋白酶活性和鱼体粗蛋白含量,各组差异有统计学意义(P0.05),而深海鱼油和鱼肝油可以显著提高肠脂肪酶活性(P0.05)。结果表明,3种强化剂各具优点,均可用于龙虎斑仔稚鱼生物饵料的强化,尤其以深海鱼油提高存活率最显著。     

不同天然饵料对凡纳滨对虾亲虾性腺发育的影响

分别以双齿围沙蚕(Perinereis aibuhitensis)、杜氏枪乌贼(Loligo duvaucelii)、近江牡蛎(Ostrea riuularis)及三者的混合饵料(1∶1∶1)培育凡纳滨对虾(Litopenaeus vannamei)亲虾至性腺发育成熟,通过分析亲虾性腺发育时间、蜕壳间期、交配率、产卵量、变态率,确定培育亲虾的优质饵料。结果表明:投喂双齿围沙蚕或混合饵料的组与投喂杜氏枪乌贼、近江牡蛎组在产卵量、卵巢发育时间、蜕壳间期、交配率、孵化率、变态率方面具有显著差异(P<0.01)。投喂双齿围沙蚕或混合饵料的亲虾平均产卵量可达21.2×104粒/尾,卵巢平均发育时间为101 h,平均蜕壳间期为218 h,平均交配率可达80%,平均孵化率可达62.99%,平均变态率可达82.44%。表明在凡纳滨对虾亲虾培育的过程中,沙蚕单独或与其他天然饵料混合投喂,较乌贼、牡蛎单独投喂对亲虾性腺发育具有更好的促进效果。