Application of probiotics as a management tool for the microbial community and the cultivation of Litopenaeus vannamei in a biofloc system
Author: Bárbara Linhares Hostins (Currículo Lattes)
Supervisor: Dr Wilson Francisco Britto Wasielesky Junior
Co-supervisor: Dra Dionéia Evangelista Cesar (UFJF)
Co-supervisor: Dr Peter Bossier (Universidade de Ghent/Bélgica)
Abstract
This thesis aimed to evaluate the influence of the addition of probiotics on bacterial density, zootechnical performance and resistance to diseases during the production of Litopenaeus vannamei. The first chapter aimed to define the appropriate application time of the post-chlorination / dechlorination probiotic of water, simulating the preparation phase that precedes the storage of the shrimp; In addition, the influence of Bacillus sp. on the density of Vibrio sp. It is recommended to apply probiotics immediately after disinfecting the water, and that fertilization with organic carbon starts 24 hours after chlorination / dechlorination of the water. By adopting such procedures, it is possible to obtain a reduction in Vibrio sp.The second chapter evaluated the influence of the operating mode of the biofloc system on protection against Acute Hepatopancreas Necrosis (AHPND). L. vannamei post larvae were cultivated in 2 types of bioflocs, Autotrophic and Heterotrophic, with and without probiotics. After 21 days, the prawns were challenged with AHPND pathogen in clear water and bioflocs corresponding to each treatment. After 96 hours, a protective effect of heterotrophic and autotrophic bioflocs with probiotics was observed, evidenced by survival rates. The third chapter evaluated the effects of supplementation with probiotics on reducing histopathological lesions in the hepatopancreas (PH) caused by an outbreak of vibriosis, and comparing them in bioflocs and clear water. After 30 days,a reduction in HP lesions was observed in probiotic treatments, in addition to better zootechnical performance and shrimp survival. The fourth chapter compared the effects of probiotics on the density of Bacillus and Vibrio spp. in the intestinal tract of shrimp grown in bioflocs and clear water. It was found that the use of probiotics reduced the density of Vibrio sp., While the abundance of Bacillus increased. The fifth chapter aimed to identify the dose-response effects of including probiotics in the diet of shrimp in the fattening phase. It is suggested that applying 3 g of probiotic per kg of feed, in two daily feeds contributed to better survival and reduction in Vibrio density. In addition, bioflocs play a probiotic function, considering the presence of B.subtilis in the water and intestinal tract at the beginning of the experiment. The results obtained in the present study contribute to the understanding of microbial ecology in the biofloc system, which is a key point for the development of this cultivation system.