Search

Five isonitrogenous and isolipidic diets were prepared with different inclusion levels of Gracilaria domingensis (GD; 0%, 5%, 10%, 15%, and 20%) with the objective to test its effects on growth and mullet immune system. The experimental diets were fed to juvenile mullet (Mugil liza, 0.42 ± 0.03g) for 60 days. The growth and expression of anti-CD3 and anti-CD4 primary antibodies for T lymphocytes were evaluated. Fish growth and feed conversion ratio decreased insignificantly by increasing GD levels up to 10% level, after which fish growth was significantly retarded. On the other hand, no significant difference was observed in granulocytes, lymphocytes, and monocytes values due to GD supplementation. Mullet fed with GD-enriched diets had a higher expression of anti-CD3 and anti-CD4 antibodies than those fed the control diet. It is concluded that a 5% inclusion level of G. domingensis in the diet increases immune competence without compromising fish growth. [ABSTRACT FROM AUTHOR]

Background: knowing the essential amino acid (EAA) requirement values is fundamental to formulate good quality and cost-effective fish feeds. However, such requirements have been established for few fish species. The estimation of amino acid requirements based on amino acid composition of fish is a fast and reliable alternative. Objective: to determine whole-body and muscle amino acid composition of Plata pompano (Trachinotus marginatus) and estimate its EAA requirements. Methods: EAA requirements were estimated using A/E ratios [(Individual EAA/Total EAA) * 1000]. Results: hystidine, leucine, lysine and phenylalanine were present in higher concentrations in muscle tissue in comparison with the whole-body. On the other hand, arginine, isoleucine, methionine, tryptophan and valine concentration were not different between whole-body and muscle. A/E ratios for Plata pompano determined in the present study are similar to those reported in other fish species, although valine A/E ratios were slightly smaller. Conclusion: until dose-response experiments are conducted to precisely determine EAA requirements, the estimated EAA values using whole-body EAA-as proposed in this study-could be used to formulate diets for Plata pompano. [ABSTRACT FROM AUTHOR]

The study aimed to evaluate the use of increasing levels of defatted rice bran fermented by Rhizopus oryzae in the diets of juveniles of mullet fish Mugil liza , assessing growth parameters, proximal carcass composition, and lipid peroxidation (TBARS) in the liver and intestine. Six experimental diets were formulated: a control treatment without rice bran, a second treatment with the inclusion of 200 g kg−1 of defatted rice bran without fermentation (DRB200), and the remaining treatments received diets with the inclusion of 100, 200, 300, or 400 g kg−1 of fermented bran. The experimental design used 216 mullet juveniles (2.10 ± 0.04 g) randomly distributed in a recirculation system composed of 18 tanks, divided into six treatments and three replications, with 12 fish per experimental unit. During the experiment, fish were fed ad libitum three times a day, for 50 days. No mortalities were recorded during the experimentation. The performance variables showed that an inclusion equal or higher than 200 g kg−1 of fermented rice bran resulted in decreased growth. Furthermore, in carcass proximal composition, the lipid content decreased with higher inclusion levels of fermented rice bran and the control treatment showed the highest lipid content, while the ash content of fish carcasses increased with the higher inclusion of the tested ingredient. No differences were recorded for TBARS in the liver and intestine. According to the results, we recommend a maximum inclusion of 100 g kg−1 fermented rice bran in diets for M. liza juveniles. • Fermentation of rice bran by Rhizopus oryzae fungus improved by 32% the amount of protein. • Defatted Rice Bran fermented can be included up to 100 g kg−1 for mullet without compromising growth performance. • Inclusions equal to or greater than 200 g kg-1 have an adverse effect on growth, but not on flesh quality. [ABSTRACT FROM AUTHOR]

Aquaculture is an important sector of world food production for which the source of protein for commercial diets is a huge bottleneck. Vegetable proteins are cheaper, but are accompanied by antinutritional compounds like phytate. Phytases are enzymes produced in microorganisms capable of degrading phytate. The addition of purified phytases to commercial feed improves the nutrient bioavailability of vegetable matter. However, the production and purification of phytases has a high cost. An alternative is to genetically manipulate a probiotic bacterium to produce and secrete phytase directly into the host's digestive tract. In the present study, a strain of Bacillus subtilis was engineered to produce and secrete a fungal phytase. The fish fed with a high vegetable content supplemented with transgenic probiotic showed an improvement in the parameters analysed. These results were corroborated with the expression of genes related to peptide transport (slc15a1b and slc15a2), appetite (ghrl), somatic growth (igf1 , myod and myog) and bone metabolism (bglap). All the analysed genes were strongly induced in the group of fish treated with the transgenic probiotic, corroborating with the results observed for the parameters. This study shows, for the first time, that a transgenic probiotic expressing recombinant phytase is able to minimize the antinutritional effects of the high content of vegetal matter included in the fish diet. The results presented herein open the possibility of transgenic probiotics being used as bioreactors for the production of molecules capable of interfering in other physiological systems in fish. • Protein for commercial diets is a huge bottleneck for aquaculture. • Plant proteins are accompanied by antinutritional compounds such as phytate. • Phytases improve the nutrient bioavailability of vegetable matter. • Since phytases have high cost, probiotic bacteria can be manipulated for enzyme secretion. • GM Bacillus subtilis minimized the antinutritional effects of phytate in zebrafish diet. [ABSTRACT FROM AUTHOR]