Improvement of Ctenopharyngodon idella reproduction technology under the conditions of water fish fishery

Author(s):  
I. Nikishkin ◽  
L. Zakonnova

The most rational way to reduce the eutrophic load on reservoirs-coolers of energy enterprises, in which the technological processes of energy production and growing fish products are not disrupted, is the introduction of fish-reclaimers into the reservoir. In this regard, full-system fisheries of this type include the production of fish-planting material of herbivorous species, in particular grass carp Ctenopharyngodon idella in their work plan. In the production conditions of Belovsky Fisheries LLC, a technology for growing planting material and commercial products of the white Amur has been developed, which has fully justified itself. At the same time, certain difficulties are associated with obtaining high-quality sexual products of herbivorous fish. Due to the technological features and hydrochemical regime of the reservoir, the production of plant-eating fish planting material is carried out with a high risk of over-aging of sexual products. Analysis of the results of spawning campaigns revealed a number of problems, including: zero percent of fertilization, early maturation and release of part of the eggs by females after a permissive injection, and gonad thrombosis. To solve the problem of low fertilization rate, special attention should be paid to sufficient oxygen concentration in water during pre-spawning operations with producers of Cupid. The problem of over-aging of sexual products and gonad thrombosis is proposed to be solved by using a flexible scheme of hormonal stimulation of producers.

Vaccines ◽  
2021 ◽  
Vol 9 (1) ◽  
pp. 41
Author(s):  
Changyong Mu ◽  
Qiwang Zhong ◽  
Yan Meng ◽  
Yong Zhou ◽  
Nan Jiang ◽  
...  

The grass carp reovirus (GCRV) causes severe hemorrhagic disease with high mortality and leads to serious economic losses in the grass carp (Ctenopharyngodon idella) industry in China. Oral vaccine has been proven to be an effective method to provide protection against fish viruses. In this study, a recombinant baculovirus BmNPV-VP35-VP4 was generated to express VP35 and VP4 proteins from GCRV type Ⅱ via Bac-to-Bac baculovirus expression system. The expression of recombinant VP35-VP4 protein (rVP35-VP4) in Bombyx mori embryo cells (BmE) and silkworm pupae was confirmed by Western blotting and immunofluorescence assay (IFA) after infection with BmNPV-VP35-VP4. To vaccinate the grass carp by oral route, the silkworm pupae expressing the rVP35-VP4 proteins were converted into a powder after freeze-drying, added to artificial feed at 5% and fed to grass carp (18 ± 1.5 g) for six weeks, and the immune response and protective efficacy in grass carp after oral vaccination trial was thoroughly investigated. This included blood cell counting and classification, serum antibody titer detection, immune-related gene expression and the relative percent survival rate in immunized grass carp. The results of blood cell counts show that the number of white blood cells in the peripheral blood of immunized grass carp increased significantly from 14 to 28 days post-immunization (dpi). The differential leukocyte count of neutrophils and monocytes were significantly higher than those in the control group at 14 dpi. Additionally, the number of lymphocytes increased significantly and reached a peak at 28 dpi. The serum antibody levels were significantly increased at Day 14 and continued until 42 days post-vaccination. The mRNA expression levels of immune-related genes (IFN-1, TLR22, IL-1β, MHC I, Mx and IgM) were significantly upregulated in liver, spleen, kidney and hindgut after immunization. Four weeks post-immunization, fish were challenged with virulent GCRV by intraperitoneal injection. The results of this challenge study show that orally immunized group exhibited a survival rate of 60% and relative percent survival (RPS) of 56%, whereas the control group had a survival rate of 13% and RPS of 4%. Taken together, our results demonstrate that the silkworm pupae powder containing baculovirus-expressed VP35-VP4 proteins could induce both non-specific and specific immune responses and protect grass carp against GCRV infection, suggesting it could be used as an oral vaccine.


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