Effects of bioprocessed soybean meal and nucleotide supplementation on growth, physiology and histomorphology in largemouth bass, Micropterus salmoides, juveniles.

In this 8-week feeding trial, the effects of nucleotide (N) supplementation (at 0.05%) were compared in diets with conventional soybean meal (CSBM or CSBM + N) versus bioprocessed SBM (BSBM or BSMB + N) on largemouth bass, Micropterus salmoides, juveniles. A total of five isonitrogenous and isolipidic diets were formulated, with the control diet being fishmeal-based. Growth, feeding efficiency, proximate composition, hepatic expression of genes involved in lipid metabolism and growth as well as liver/intestinal histopathology were assessed. Results showed that growth was significantly higher in fish fed the control diet, but there was no significant effect of SBM type or nucleotide supplementation on growth, feeding efficiency, or proximate composition. Hepatic expression of growth hormone (GH), insulin-like growth factor I (IGFI), superoxide dismutase (SOD), fatty acid synthase (FASN) and cholesterol 7 alpha-hydroxylase (CYP7A1) were unaffected by the diets. Tumor necrosis factor alpha (TNF-α) and transforming growth factor beta (TGF-ß) were significantly downregulated and upregulated, respectively, in the SBM-based treatments compared with the control. The intestinal villi were significantly shorter and wider in fish fed the CSBM diet compared to the other treatments. The villi height and width were similar between the control and those fed the BSMB + N diet. It may be possible that the unaffected growth by nucleotides were due to an insufficient dose and/or undisrupted nucleotide synthesis due to being cultured under good conditions. Meanwhile, the unaffected growth in the SBM treatment could indicate a tolerance of M. salmoides to plant proteins and associated antinutritional factors. Nevertheless, BSBM and/or nucleotides appeared to mitigate some adverse effects of dietary SBM to the intestinal histomorphology in M. salmoides.

Effects of Schizochytrium and micro-minerals on immune, antioxidant, inflammatory and lipid-metabolism status of Micropterus salmoides fed high- and low-fishmeal diets.

A 12-week factorial experiment was conducted to investigate the interactive effects of dietary algal meal (Schizochytrium sp., AM) and micro-minerals (MM, either organic [OM] or inorganic [IM]) on the immune and antioxidant status, and the expression of hepatic genes involved in the regulation of antioxidants, inflammatory cytokines, lipid metabolism, and organ growth of largemouth bass (LMB; Micropterus salmoides) fed high-and low-fishmeal (FM) diets. For this purpose, two sets of six iso-nitrogenous (42% crude protein) and iso-lipidic (12% lipid) diets, such as high (35%) and low (10%) FM diets were formulated. Within each FM level, AM was used to replace 50% or 100% of fish oil (FO), or without AM (FO control) and supplemented with either OM or IM (Fe, Zn, Mn, Cu, and Se). Diets were fed to juvenile LMB (initial weight, 25.87 ± 0.08 g) to near satiation twice daily. The results indicated that FO replacement by dietary AM did not change the levels of most biochemical (ALB, AMY, TP and GLOB), antioxidants (SOD, GPx and GSH), and immune (IgM and lysozyme) parameters in LMB, except ALP and CAT. MM affected only hepatic GSH, with lower values in fish fed the OM diets. FM influenced the levels of ALP, AMY, GLOB, IgM, and MDA (P < 0.05). A three-way interactive effect (P = 0.016) was found on IgM only, with lower levels in fish fed diet 12 (low-FM, AM100, OM). Subsequently, the relative expressions of hepatic antioxidants (Cu/Zn-SOD and GPx-4), inflammatory cytokines (TNF-α and TGF-ß1), lipid metabolism (FASN and CYP7A1), and organ growth (IGF-I) related genes were affected by the dietary treatments, with interactions being present in Cu/Zn-SOD, TNF-α, TGF-ß1, FASN and IGF-I. Overall, dietary AM could be used as an alternative to FO in low-FM diets without compromising the health of LMB, especially when it is supplemented with MM.

ß-1,3 glucan derived from Euglena gracilis and Algamune™ enhances innate immune responses of red drum (Sciaenops ocellatus L.).

To reduce susceptibility to stressors and diseases, immune-modulators such as ß-glucans have been proven effective tools to enhance the innate immune responses of fish. Consequently, commercial sources of this polysaccharide are becoming increasingly more available. Algamune™ is a commercial additive produced from Euglena gracilis, as a source of linear ß-1,3-glucan. In order to evaluate the immunomodulatory effects of this ß-glucan product, the present study assessed the innate immune parameters of red drum (Sciaenops ocellatus) exposed to Algamune™ ex vivo and in vivo. Isolated kidney phagocytes were incubated with graded concentrations (0, 0.2, 0.4, 0.8, 1.6 and 3.2 mg L-1) of dried Euglena gracilis (Algamune™) as well as purified Paramylon (linear ß-1,3 glucan). Increased bactericidal activity against Streptococcus iniae, and production of intracellular O2- anion superoxide were stimulated by both ß-glucan sources. A reduced activity of extracellular anion superoxide was observed by the phagocytes incubated with Algamune ™. After corroborating the effectiveness of the glucan source ex vivo, a feeding trial was conducted using red drum juveniles (∼26.6 g initial weight). Fish were fed diets with graded levels of Algamune™ (0, 100, 200, 400 and 800 mg kg-1) twice daily for 21 days. No significant differences were detected regarding production performance parameters. At the end of the feeding trial, blood, intestinal content, and kidney were sampled. Intestinal microbiota from fecal material was analyzed through denaturing gradient gel electrophoresis (DGGE) and found to be similar among all treatments. No significant differences were detected for oxidative radical production from whole blood, and isolated phagocytes, and plasma lysozyme activity. However, the total hemolytic activity of red drum plasma was increased in fish fed 100 and 200 mg kg-1 of dietary Algamune™ when compared to fish fed the basal diet. Based on results from both ex vivo and in vivo trials, ß-glucan from Algamune™ was demonstrated to have a moderate immunostimulatory effects on red drum.