Performance of the nile tilapia with varying daily feeding amounts, using a commercial diet / Desempenho da Tilápia do Nilo com variação diária de alimentação, usando dietas comerciais

In order to evaluate the performance of Nile tilapia (Oreochromis niloticus), daily feeding amounts were varied in an experiment following a completely randomized design for 154 days and consisting of four treatments with three replications each, totaling 12 tanks with 3 m3 (3 x 1 x 1 m) of area each at densities of 5 fish m-3 (initial) and 3 fish m-3 until the end of the experiment. Throughout the experimental period, the daily amount of feed was varied and delimited for each feeding time (8h00, 11h00, 14h00 and 17h00) as: 25; 25; 25 and 25% in daily treatment 1 - T1; 20; 30; 30 and 20% in treatment 2 - T2; 30; 20; 20 and 30% in daily treatment 3 - T3; and 20; 30; 20 and 30% in treatment 4 - T4. Feed was offered six days a week, with extruded isocaloric (1,412 KJ) and isoproteic (32% crude protein) diets from 2 to 4 mm. Every two weeks, a sample containing 30% of stocked individuals was collected in each replication to monitor fish growth. Nile tilapia (O. niloticus) fed in daily amounts of 20; 30; 20 and 30% showed a better growth performance in the final of experiment, mainly on biomass, final average weight and feed conversion.

Para avaliar o desempenho da tilápia do Nilo (Oreochromis niloticus), as quantidades diárias de alimentação foram variadas em um experimento após um delineamento inteiramente casualizado de 154 dias e consistindo em quatro tratamentos com três repetições cada, totalizando 12 tanques com 3 m3 (3 x 1 x 1 m) de área cada uma em densidades de 5 peixes m-3 (inicial) e 3 peixes m-3 até o final do experimento. Ao longo do período experimental, a quantidade diária de alimentos foi variada e delimitada para cada tempo de alimentação (8h00, 11h00, 14h00 e 17h00) como: 25; 25; 25 e 25% no tratamento diário 1 - T1; 20; 30; 30 e 20% no tratamento 2 - T2; 30; 20; 20 e 30% no tratamento diário 3 - T3; e 20; 30; 20 e 30% no tratamento 4 - T4. O alimento foi oferecido seis dias por semana, com dietas isocalóricas extrudadas (1.412 KJ) e isoprotéicas (32% de proteínas brutas) de 2 a 4 mm. A cada duas semanas, uma amostra contendo 30% de indivíduos estocados foi coletada em cada replicação para monitorar o crescimento do peixe. Tilápias do Nilo (O. niloticus) alimentadas em quantidades diárias de 20; 30; 20 e 30% mostraram um melhor desempenho de crescimento no final do experimento, principalmente na biomassa, peso médio final e conversão alimentar.

Potential immunomodulatory and protective effects of the Arthrospira-based dietary supplement on shrimp intestinal immune defenses.

Herein, we evaluated the immunomodulatory and the antiviral protective properties of a cyanobacteria-enriched diet on the immune responses of the Pacific white shrimp Litopenaeus vannamei challenged with the White spot syndrome virus (WSSV). Shrimp were fed with an Arthrospira platensis supplemented feed during 20 days, and its effects were examined by evaluating well-known standardized shrimp immune parameters (total hemocyte counts, total protein concentration, phenoloxidase activity, and serum agglutination titer). Additionally, we assessed the expression of crucial genes involved in both hemolymph- and gut-based immunities related to the shrimp capacity to circumvent viral and microbial infections. Dietary supplementation improved shrimp survival rates after challenge with a median lethal dose of WSSV. From all immune parameters tested, only the serum agglutination titer was higher in treated animals. On the other hand, the expression of some representative marker genes from different immune response pathways was only modulated in the midgut and not in the circulating hemocytes, suggesting that this feed supplementation can be used as an attractive strategy to enhance immunity in shrimp gut. Altogether, our results evidence the immunomodulatory properties of A. platensis supplemented feed in shrimp humoral and intestinal defenses and highlight the potential use of cyanobacteria-based immunostimulants in shrimp farming for protection against infectious diseases.