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Taurine is considered a conditionally essential amino acid for fish, so its supplementation may improve feed conversion. This study evaluated the supplementation of taurine on growth performance, hematological and immunological parameters, production costs, and survival of Nile tilapia (Oreochromis niloticus) juveniles raised in a recirculating aquaculture system (RAS). A control diet was formulated with 360 g kg-1 of crude protein without fish meal and without taurine supplementation (Control). From the control diet, another diet supplemented with 9.7 g of taurine per kg of feed (Taurine) was produced. Fish fed diet supplemented with taurine had lower daily average weight gain and final average weight compared to the control diet (p < 0.05). It was observed that taurine had no influence on condition factor, survival, or hemato-immunological parameters of Nile tilapia juveniles, but there was a higher mean corpuscular volume and greater nitrogen retention in fish from the control group (p < 0.05). It is concluded that Nile tilapia juveniles do not benefit from taurine supplementation in RAS, even when fed diet containing plant-based protein sources.

The objective of this work was to evaluate the effect of autochthonous and allochthonous lactic acid bacteria (LAB) in two species of lambaris (Astyanax bimaculatus and Astyanax fasciatus), and to investigate the effects on intestinal microbiota and hematological changes. Two experiments were carried out, one for each lambari species, both assays were divided into three treatments: autochthonous LAB, allochthonous LAB and control. The 10% inoculum was included on diet in the LAB treatments and sterile medium for control. After 30 days for A. bimaculatus LAB indigenous changes all bacteria groups analyzed, while allochthonous LAB just decrease Staphylococcus spp. count. Though for A. fasciatus his autochthone LAB reduced the staphylococcal count. In hematology, for A. bimaculatus autochthonous LAB showed a higher number of thrombocytes, lymphocytes, monocytes and total leukocytes in the circulatory system than the control. Though for A. fasciatus his autochthone LAB showed a higher number of total lymphocytes and leukocytes than the control, while Lactobacillus sp. acting as an allochthone, it did not differ among treatments. In conclusion, both LAB (Lactobacillus sp. and L. lactis) promoted more beneficial changes in the microbiota and hematological profile when they act as an autochthone probiotic, demonstrating a probiotic-associated host.

This study aimed to evaluate the effects of the dietary supplementation Curcuma longa hydrolate on Nile tilapia (Oreochromis niloticus) reared in a recirculation system. Hemato-immunological parameters, growth performance, nitrogen and phosphorus retention, as well as body composition and its interaction with the intestinal microbiota, were studied. Nile tilapia fingerlings (120) were distributed randomly in 8 polyethylene tanks (40 L). The experimental units were divided into two treatments, in quadruplicate: commercial diet supplemented with 2.5% of C. longa hydrolate and commercial diet without supplementation (control). After 45 days, the treatment supplemented hydrolate showed higher survival than the control group, 95.25% and 82.22%, receptively. In the blood profile, fish supplemented with hydrolate had a higher count of total leukocytes and neutrophils, as well as mean corpuscular hemoglobin and mean corpuscular hemoglobin concentration, than control group. The hydrolate group showed a substantial increase in the relative abundance of Cetobacterium and Romboutsia, as well as lower diversity in gut microbiota. The dietary addition of C. longa hydrolate for Nile tilapia seems to have a beneficial effect on gut microbiota, in addition to a likely positive effect on the physiological performance of Nile tilapia by maintaining intestinal homeostasis and promoting survival in reared conditions.