Use of resistant and fast-growing post-larvae of the shrimp Litopenaeus vannamei in cultivation in a biofloc system
With the growth and intensification of shrimp farming, the sector has been suffering from problems related to the onset and spread of diseases. Currently the white spot syndrome virus (WSSV) is one of the diseases that most devastate shrimp productions around the world. The strategies adopted to cope with or eliminate the virus from the growing environment are the use of high-level biosafety production systems (BFT System), use of low stocking densities, use of specific pathogen-free organisms, as well as genetically improved organisms to resist disease. The present study had as objective to evaluate the zootechnical and immunological performance of two Litopenaeus vannamei strains (strain of fast growth and resistance to WSSV) in different culture conditions, such as: direct stocking of post-larvae and biphasic system; cultivation at different stocking densities; cultivation in clear water x BFT. Four experiments were carried out at the Marine Aquaculture Station (Oceanography Institute - FURG): (1) Superintensive culture (400 shr.m-2) of the two strains of L. vannamei in BFT system with direct storage and biphasic system; (2) Intensive culture (105 shr.m-2) of the two strains of L. vannamei in BFT system; (3) Low density culture (8 and 24 shr.m-2) of the two strains of L. vannamei in BFT system; (4) Super-intensive cultivation (222 shr.m-2) of the two strains of L. vannamei in BFT system and in a clear water system. The fast- growing strain obtained a better zootechnical performance compared to the white spot resistance strain in all experiments. In the experiment 1, the direct storage favored the best growth of the shrimp of the fast growing strain, being impaired in the biphasic system, which did not occur in the WSSV resistance strain. In experiment 2, in an intensive system, the fast-growing strain was better in relation to the resistance strain. The low stocking densities tested in experiment 3 contributed to the higher weight gain of both strains, being more expressive in the shrimp of the fast-growing strain cultured at 8 shr.m-2 density. In the fourth experiment, the fast growing lineage obtained a better zootechnical performance, not being observed weight differences in the shrimps of the same lineages grown in different systems (BFT or clear water). The different strains of L. vannamei showed no differences in their immunological condition.