Influence of Different Protein and Lipid Levels in Diets of Litopenaeus vannamei Shrimps Cultivated in Superintensive Biofloc Systems
Author: Ítalo Felipe Mascena Braga (Currículo Lattes)
Advisor: Dr. Geraldo Kipper Fóes
Abstract
The increasing demand for high-quality proteins, coupled with the need to reduce land and water use, has intensified interest in the cultivation of aquatic organisms. In this context, the Pacific white shrimp, Litopenaeus vannamei, is an excellent candidate. Its set of biological characteristics enables adaptation to various conditions and culture systems, including high tolerance to superintensive biofloc systems. However, increasing stocking density may negatively affect growth, feed efficiency, and may lead to increased intraspecific competition, as well as impair the immune system and antioxidant capacity of the animals. Nutrition can serve as a tool to mitigate the problems associated with high stocking density, specifically through the use of diets tailored for superintensive cultures (nutritionally and energetically), which can enhance growth and profitability. This dissertation is composed of four chapters addressing the rearing of shrimp in superintensive biofloc systems under the influence of different protein and lipid levels during the nursery and grow-out phases. Experimental studies were conducted in biofloc systems (50 L working volume) to assess the influence of different diets on water quality variables, zootechnical performance, antioxidant capacity of the animals, and the nutritional quality of both bioflocs and shrimp. In Chapter I, different dietary protein levels (32, 36, 40, 44, and 48%) were tested during the nursery phase of L. vannamei. Diets rich in crude protein (44 and 48% CP) increased alkalinity consumption and consequently reduced pH in the treatments (p<0.05); additionally, in the 48% CP treatment, elevated nitrite levels and increased water consumption were observed. Nevertheless, the biofloc system proved effective in reducing the protein levels in the shrimp diets to as low as 32% CP without affecting growth, survival, or antioxidant system of the animals (p>0.05). In Chapter II, different dietary lipid levels (5.0, 7.0, 9.0, 11, and 13%) were tested for the nursery phase of L. vannamei. The results indicate that diets with lipid content above 9.0% significantly reduced survival and productivity, in addition to increasing feed costs during this phase (p<0.05). The lipid content of the biofloc nutritional composition was directly proportional to the lipid levels in the diets (p<0.05). Chapter III evaluated different dietary protein levels during the grow-out phase. It is possible to reduce dietary protein levels to 36% CP without compromising the zootechnical performance of the animals (p>0.05); regression and broken-line models applied showed that the optimal protein levels in the diets are 46.3% and 38.2% CP, respectively. Furthermore, feed costs were higher in the 32% CP treatment (p<0.05). In Chapter IV, different dietary lipid levels were tested during the grow-out phase of L. vannamei. Diets containing 5.0% and 7.0% lipids provided better survival rates, feed utilization, and nutrient retention (p<0.05). Moreover, the highest lipid levels tested (9.0, 11, and 13% EE) negatively affected pH and lipid oxidation over storage time. Our results allow us to conclude that the use of specific diets for superintensive biofloc culture systems can maximize zootechnical performance without compromising water quality or the animals’ antioxidant systems, in addition to reducing feed costs.