新型饲料添加剂对对虾生长和免疫力的影响

[目的]研究新型饲料添加剂对对虾生长和免疫力的影响。[方法]以初始体质量为(0.52±0.08)g的对虾为研究对象,探讨新型添加剂对对虾生长和免疫力的影响。试验设置2个试验组(A、B)组和1个对照组(C组)分别投喂饲料:对照组为对虾专用饲料,A组为在对虾专用饲料中添加1%新型饲料添加剂,B组为在对虾专用饲料中添加2%新型饲料添加剂。[结果]新型饲料添加剂可提高对虾存活率和增重率,降低饲料系数。当新型饲料添加剂添加量为2%,可显著促进对虾生长;试验组的酚氧化酶(PO)、超氧化歧化酶(SOD)、溶菌酶(LSZ)活力均高于对照组。[结论]新型饲料添加剂具有促进对虾生长和提高免疫力的作用,其最佳添加量为2.0%。     

基于TAM-TPB理论的农户生态农业技术采纳意愿研究--以稻虾共作技术为例

随着经济社会的发展,环境污染和资源浪费问题不断涌现,在农业生产方面表现得尤为突出,而生态农业技术的采纳是缓解生态压力的前提基础。本文基于技术接受模型-计划行为理论(TAM-TPB),利用湖北、湖南、安徽三省的调研数据,采用二元Logit回归模型,实证分析了农户稻虾共作技术采纳意愿的影响因素。结果表明:①农户采纳稻虾共作技术的意愿主要受到行为态度、主观规范、知觉行为控制、感知有用性和感知易用性的显著正向影响。其中,主观规范和知觉行为控制是影响农户采纳意愿的直接因素。②感知有用性、感知易用性对农户采纳意愿有直接影响,且以行为态度为中介变量产生间接影响,呈正向作用。鉴于此,本文提出相关建议,建议有关部门集中宣讲稻虾共作技术的综合效益;建议农技部门给农户提供技术帮助;建议村委会定期组织农户间交流。     

Postlarvae and juveniles of a selected line of Penaeus stylirostris are resistant to infectious hypodermal and hematopoietic necrosis virus infection

A susceptibility study of postlarvae (PL) and juvenile Super Shrimp®, a selected line of Penaeus stylirostris, was conducted to compare their resistance to infectious hypodermal and hematopoietic necrosis virus (IHHNV) infection to that of a specific pathogen free (SPF) population of P. vannamei. Super Shrimp® PLs were fed with IHHNV-infected shrimp tissue for 2 days and then maintained on a pelletized ration for an additional 28 days. PLs were sampled at days 0, 1, 2, 3, 4, 6, 10, 15, 20, 25 and 30. There was no apparent mortality during the experimental period. Tissue DNA extracted from the PLs was analyzed for the presence of IHHNV by PCR. Low levels of IHHNV were detected only in DNA extracts from samples at days 1, 2, and 3. No IHHNV DNA was detected from days 4 to 30. The days that the PLs were weakly IHHNV-PCR positive were during the period that they were being fed with IHHNV-tissue, and thus, the IHHNV DNA signal was suspected to be from the infected tissue used as a feed. Through both histology and in situ hybridization, we confirmed that tissues of Super Shrimp® PLs were not infected with IHHNV. PCR results of another IHHNV challenge study with juveniles of Super Shrimp® were similar to those with PLs. These results indicate that IHHNV did not replicate in the PL and juvenile Super Shrimp®. In contrast, P. vannamei juveniles, which were used as a positive control, showed a more intense IHHNV infection, as determined by PCR detection, beginning at 6 days postchallenge and increasing throughout the remainder of the study. In addition, the IHHNV-infected P. vannamei at 30 days postchallenge showed histological changes characteristic of IHHNV infection and had a positive reaction for IHHNV with in situ hybridization. Our studies show that Super Shrimp® are resistant to IHHNV infection. This is the first unequivocal demonstration of resistance to viral infection in shrimp.     

对虾配合饲料水中稳定性的影响因素及其测定方法

阐述了对虾配合饲料水中稳定性的概念及其重要性;分析了影响配合饲料水中稳定性的内在因素为生产原料、生产工艺和粘合剂,外在因素为养殖水环境。综述了对虾配合饲料水中稳定性的４种测试方法：感官法、干燥称重法、化学耗氧量法和光度法,深入讨论了各种测试方法的优缺点,指出了中华人民共和国标准方法中存在的问题与不足。提出了今后对虾配合饲料在水中稳定性研究方面应重点解决的问题。     

对虾白斑综合征病毒(WSSV)高分子量结构蛋白的分离

采用蔗糖密度梯度离心从患病对虾组织中提取WSSV,应用SDS-PAGE对WSSV结构蛋白进行了分析。采用12％分离胶,将WSSV样品煮沸5min,应用SDS-PAGE分离了WSSV的中低分子量结构蛋白,并将该结果与其他学者已发表的结果进行了比较。首次通过延长样品煮沸时间,采用8％分离胶,应用SDS-PAGE分离到了WSSV100kD以上的13条高分子量结构蛋白,计算出了每条蛋白带的分子量及其在总蛋白中的百分含量。其中WSSV高分子量结构蛋白的分离丰富了WSSV的研究范围,对今后深入的研究工作具有重要意义。     

女山湖虾类资源的合理利用与增殖

介绍了女山湖的虾类组成及青虾和秀丽白虾在该湖的生态分布与繁殖特点；同时对该湖的虾业现状进行了分析。在此基础上提出了合理利用与增殖虾类资源的建议。     

A soft technology to improve survival and reproductive performance of Litopenaeus stylirostris by counterbalancing physiological disturbances associated with handling stress

The consequences of handling stress (fishing, transfer, eyestalk ablation) on shrimp broodstock are poorly documented. The weakness of farmed shrimp, Litopenaeus stylirostris, during winter is a major problem in New Caledonia, because of seasonal climate (tropical–sub-temperate). The transfer of broodstock in winter from earthen outdoor ponds to indoor maturation tanks in the hatchery (T = 20 °C, Salinity = 35‰, fed shrimp) usually leads, after 48 h, to high mortality (up to 70%). Eyestalk ablation to induce ovarian maturation in females leads to further mortality.

Starting from a background analysis of physiological disturbances (initial osmoregulatory imbalance) associated with handling stress (Wabete, N., Chim, L., Lemaire, P., Massabuau, J.-C., 2004. Caractérisation de problèmes de physiologie respiratoire et d'échanges ioniques associés à la manipulation chez la crevette pénéide Litopenaeus stylirostris à 20 °C. Styli 2003. Trente ans de crevetticulture en Nouvelle-Calédonie. Ed. Ifremer. Actes Colloq. 38, 75-84.), we developed a protocol using a soft technology, based on modifications of water salinity, temperature and feeding regime. The aim was to minimize problems of osmoregulatory imbalance and associated mortalities. The protocol we developed, called the LSD OT protocol (Low Salinity and Diet, Optimal Temperature), was first evaluated on sub-adult shrimp (20–25 g) and then applied to broodstock. Survival after transfer and following eyestalk ablation, as well as reproductive achievement (spawning rate, nauplii number) was considerably improved when shrimps were transferred under “physiological comfort” i.e. warmed isosmotic water (26 °C and 26‰) and unfed for 3 d. This new handling protocol, based on a better control of salinity, temperature and feeding conditions, has been transferred successfully to private hatcheries and already contributes to an increased profitability of New-Caledonian shrimp industry.     

Substitution of Chaetoceros muelleri by Spirulina platensis meal in diets for Litopenaeus schmitti larvae

The nutritional response of Litopenaeus schmitti larvae to substitution of Chaetoceros muelleri by Spirulina platensis meal (SPM) was evaluated. The substitution levels (S) were 0%, 25%, 50%, 75% and 100%, dry weight basis. Final larval length (FL) ranged from 1.98 to 3.16 mm for the different substitution levels. There was a significant relationship between S and FL, described by the following quadratic equation: FL = 2.853 + 0.01598S − 0.000233S². The substitution level (S) yielding maximum FL was 34.2%. Development index (DI) values ranged from 2.84 to 3.93 and were dependent on substitution level. The corresponding equation was DI = 3.799 + 0.00945S − 0.000189S² (P < 0.01). Maximum DI was obtained at 25.0% substitution. Survival was high (82–87%) and no significant differences were found between treatments. Protein digestibility of either microalgae was high, with 92% for SPM and 94% for C. muelleri, with no significant differences between them. The results in this study indicate that an adequate balance of nutrients in relation to the requirements of the species is critical. To simultaneously improve FL and DI, a 30% substitution of C. muelleri by SPM is suggested. This is equivalent to feeding 0.15 mg larvae^− 1 day^− 1 dry weight basis of a 70% C. muelleri/30% SPM diet, representing 0.078 mg protein larvae^− 1 day^− 1, 0.026 mg lipids larvae^− 1 day^− 1 and 2.732 J larvae^− 1 day^− 1.     

Production and economic return of shrimp aquaculture in coastal ponds of different sizes and with different management regimes

Coastal shrimp (Penaeus monodon) aquaculture in Bangladesh is mostly practiced in a special type of field/pond situated by the side of a river -- called a Gher -- that is used to cultivate rice in winter and shrimp in summer. Ghers of different sizes are managed in different ways. In order to understand the effects of Gher size and their corresponding management practices on the production and economic returns of shrimp farming, we conducted an on-farm study in three small (1–5 ha), three medium (6–10 ha) and three large (>10 ha) Ghers located in the coastal Southwest region of Bangladesh. The mean harvest weight of shrimp was similar in all Ghers, but survival rates were higher in the small (50%) and medium (37%) ones than in the large (18%) ones. The high mortality in the large units led to a production that was lower than one-half of that in the small Ghers (about 80 and 200 kg/ha, respectively). The total variable costs per unit area were similar in all Ghers, but the importance of different items varied with Gher size. In the small Ghers, there are relatively high investments on inputs and labor. This expenditure results in lower shrimp mortality and higher production, which in turn results in gross returns that are larger than the total costs -- hence, a positive and high net return. In large Ghers, the fixed costs are larger than in the small ones simply because of the size of the pond. Variable costs include higher investments in post-larvae and labor than in small Ghers, and lower inputs applied only at pond preparation. This results in higher shrimp mortality and lower production, which in turn results in gross returns that are smaller than the total costs -- hence, a negative or low net return. These findings have positive implications for the future policy formulation of coastal shrimp aquaculture in Bangladesh.     

Differential host passaging alters pathogenicity and induces genomic variation in white spot syndrome virus

To understand the pathological effects of passaging WSSV through different animals, we passaged WSSV through crabs (Portunus sanguinolentus and P. pelagicus), prawn (Macrobrachium rosenbergii) and artemia (Artemia sp.). Among the three geographically distinct WSSV isolates (A166, G9 and G27) that caused over 95% mortalities in experimental infections in P. monodon, only two isolates (A166 and G9) caused mortality (5%) in M. rosenbergii. On subsequent infection of P. monodon with the passage one virus (P1V) from M. rosenbergii, only P1V of A166 caused 5% mortality while P1V of G9 failed to cause any mortality, though the infected shrimp were positive for WSSV by nested PCR. Crabs showed differential susceptibility to WSSV isolates. While passaging WSSV (G9) through P. sanguinolentus retained pathogenicity, passaging through P. pelagicus completely attenuated the two strains (A117 and G27). Passaging through M. rosenbergii changed pathogenicity of isolates (A166 and G9) from 95% to 5% cumulative mortality in experimental infections. WSSV was unable to infect Artemia and could not transmit the disease to P. monodon. WSSV (A117) passaged through P. monodon retained its virulence. An examination of tandem repeats (TR) in ORF 94 of the WSSV genome revealed variations upon passaging through different hosts. One isolate (A117), with 12 TR yielded 8 TR when passaged through P. pelagicus and 18 TR when passaged through P. monodon. Two other isolates (G9 and G27) with 9 TR, retained them when passaged through P. monodon and P. sanguinolentus but yielded 8 and 12 TR when passaged through P. pelagicus and M. rosenbergii, respectively. Thus, differences in TR number appeared to result from host selection rather than geographical isolation.