Fertilization strategies for intensive farming of Penaeus vannamei using a symbiotic system
Author: Otávio Augusto Lacerda Ferreira Pimentel (Currículo Lattes)
Advisor: Dr. Dariano Krummenauer
Abstract
This thesis aimed to analyze the effect of different fertilization strategies of the synbiotic system on water quality, microbial community development, and growth of shrimp Penaeus vannamei reared at high stocking density. The first study reviewed different fertilization protocols used in the synbiotic system and what research has been done to improve the management of this system. The second study tested the effect of using different vegetable brans as an organic carbon source for the synbiotic fertilization on the nitrification process, planktonic composition, and growth of P. vannamei in the nursery phase, as well as comparing it with the biofloc system. This study recommended the use of rice bran in the synbiotic fertilization, since it promoted growth of shrimp P. vannamei similar to the biofloc and clear water systems and superior to what was found for the synbiotic fertilized with wheat bran. The rice bran still produced a high load of microorganisms in the system, mainly Bacillus. The third study evaluated the effect of fermentation and respiration processes, as well as different processing times of the synbiotic system fertilizer, on the nitrification process, plankton composition, and growth of P. vannamei during the nursery phase and compared these results with the biofloc system. In this study, processing rice bran through a fermentation phase for 12 hours followed by a microbial respiration phase for 12 hours proved to be the most effective, as it was able to control total ammonia faster, accelerating microbial loop development, increased yield, and reduced the feed conversion ratio of P. vannamei when compared to the control treatment, which used clear water. The fourth study evaluated the effect of using different probiotic microorganisms in the fertilization of the synbiotic system on the microbial community composition of the system, nitrification process, and growth of P. vannamei in the nursery phase. This study concluded that the use of probiotics composed of microorganisms of the genera Bacillus, Lactobacillus, and Pediococcus in the composition of the fertilizer provided faster control of ammonia, higher abundance of ammonia-oxidizing and nitrite-oxidizing bacteria, lower abundance of Vibrio, higher final weight of P. vannamei, higher yield, and lower feed conversion ratio. The fifth study evaluated the effect of different culture systems on water quality, planktonic composition, and growth of P. vannamei in low salinity water and high stocking density. The results showed that the synbiotic system improved the control of nitrogenous compounds, in addition to promoting the growth of more protozoan microorganisms such as ciliates and amoebas. These results were reflected in higher survival, yield, and lower feed conversion ratio of shrimp.