Leonardo Tachibana

Relação lisina digestível: proteína digestível em rações para tilápias-do-nilo

This study was carried out to determine the best digestible protein/digestible lysine ratio that should be present in feed fed to Nile tilapias. Two hundred and sixteen tilapias (11.0 ± 0.43g) were distributed in 36 fish tanks (205 L) at a density of 6 fish/tank. Twelve feeds were formulated with three different digestible protein (DP) levels 22.0; 26.0 and 30.0% (based on digestible amino acids) and four different lysine percentages of 4.5; 6.0; 7.5 or 9.0% in relation to digestible protein. The fish were fed ad libtum during a 60-day period. There was significant effect of the digestible protein and digestible lysine ratio on weight gain, because the increase in lysine levels in feeds with 26 and 30% DP promoted linear increase in this parameter. The best values for feed conversion were obtained at the levels 26 and 30% DP that increased the daily consumption of digestible protein. The lysine level caused a linear reduction in feed conversion and linear increase in the protein efficiency rate. The results suggested that the 26% DP level might be used in ration to feed Nile tilapia juveniles; however, these should contain digestible amino acids and the digestible lysine/digestible protein ratio should be 6.0%. However, for levels higher than 26% DP, a maximum digestible lysine level of 7.5% DP improved weight gain for the species.

Xilanase e β-glucanase na digestibilidade aparente de nutrientes do triticale pela Tilápia-do-nilo

The effects of different levels of Natugrain Blend L® enzymatic compound on triticale nutrients and energy digestibility by Nile tilapia were evaluated. The digestibility was indirectly determined with chromic oxide III (0.10%) as an external marker. The level of substitution by triticale in the reference diet was 50%. The treatments were 0, 150, 300, 450, and 600g kg of Natugrain Blend L, which contains 800 units g-1 of endo-1,3(4)-β-glucanase (BGU) and 36.600 units g-1 of endo-1,4-β-xylanase (EXU). The apparent digestibility coefficients were: dry matter 76.42, 74.01, 83.39, 82.97, and 78.34%; crude protein 88.19, 88.39, 90.52, 92.05, and 88.34%; crude energy 75.93, 71.31, 81.78, 80.27, and 78.62%, respectively to inclusion levels of 0.0, 150.0, 300.0, 450.0, and 600.0mg kg-1 of Natugrain Blend L in diet. Results demonstrated that 300mg kg-1 of enzymes were enough to increase the dry matter apparent digestibility coefficient and energy. The enzyme compound can be used to increase the efficiency of triticale feed utilization.

Fish pathogen bacteria: Adhesion, parameters influencing virulence and interaction with host cells

&NA; Wild fisheries are declining due to over‐fishing, climate change, pollution and marine habitat destructions among other factors, and, concomitantly, aquaculture is increasing significantly around the world. Fish infections caused by pathogenic bacteria are quite common in aquaculture, although their seriousness depends on the season. Drug‐supplemented feeds are often used to keep farmed fish free from the diseases caused by such bacteria. However, given that bacteria can survive well in aquatic environments independently of their hosts, bacterial diseases have become major impediments to aquaculture development. On the other hand, the indiscriminate uses of antimicrobial agents has led to resistant strains and the need to switch to other antibiotics, although it seems that an integrated approach that considers not only the pathogen but also the host and the environment will be the most effective method in the long‐term to improve aquatic animal health. This review covers the mechanisms of bacterial pathogenicity and details the foundations underlying the interactions occurring between pathogenic bacteria and the fish host in the aquatic environment, as well as the factors that influence virulence. Understanding and linking the different phenomena that occur from adhesion to colonization of the host will offer novel and useful means to help design suitable therapeutic strategies for disease prevention and treatment. Graphical abstract Figure. No Caption available. HighlightsFish bacterial diseases are an important problem in aquaculture.New approaches considering the interaction between the pathogen, the host and the environmental parameters are priority.Linking bacterial adhesion and fish cell responses will help to design suitable therapeutic strategies.