Hemato-Immunological Responses and Disease Resistance in Siberian Sturgeon Acipenser baerii Fed on a Supplemented Diet of Lactobacillus plantarum

Combined effects of enzymes and probiotics on hemato-biochemical parameters and immunological responses of juvenile Siberian sturgeon (Acipenser baerii)

A 10-week feeding trial was run to investigate the separate and simultaneous effects of exogenous enzymes (Enz), probiotics (Pro), and Pro-Enz mixtures on the hematology indices, serum biochemical parameters, and innate-immunity status of juvenile Siberian sturgeon. The fish (138.06 ± 3.64 g) were randomly dispersed into 12 tanks (20 individuals per tank) and fed with Enz (Phytase, protease, and xylanase), Pro (Pediococcus pentosaceus and Lactococcus lactis), and Pro-Enz cocktail. At the end of the feeding bioassay, the highest values of red blood cell count, hemoglobin concentration, hematocrit level, and lymphocyte percentage followed by the lowest neutrophil percentage were obtained in Pro-Enz treatment (P < 0.05). Despite a significantly lower level of alkaline phosphatase in the fish fed with Pro supplemented diet (P < 0.05), no significant difference was found in the serum level of alanine aminotransferase and aspartate aminotransferase among the experimental groups (P > 0.05). Total protein content was significantly upregulated in serum and skin mucus samples from those fed with supplemented diets compared to the control group (P < 0.05). In both serum and skin mucus samples, higher immune responses in terms of lysozyme activity, immunoglobulin M, total protein was seen in Pro-Enz treatment compared to the control group followed by the serum complement components (P < 0.05). The results indicate that the combinational supplementation of Siberian sturgeon diet with the exogenous enzymes and probiotics modulates the physiometabolic responses and innate immune system to a higher grade than their individual supplementation.

Bacteriome Structure, Function, and Probiotics in Fish Larviculture: The Good, the Bad, and the Gaps

Aquaculture is the fastest-growing sector in food production worldwide. For decades, research on animal physiology, nutrition, and behavior established the foundations of best practices in land-based fish rearing and disease control. Current DNA sequencing, bioinformatics, and data science technologies now allow deep investigations of host-associated microbiomes in a tractable fashion. Adequate use of these technologies can illuminate microbiome dynamics and aid the engineering of microbiome-based solutions to disease prevention in an unprecedented manner. This review examines molecular studies of bacterial diversity, function, and host immunitymodulation at early stages of fish development, where microbial infections cause important economic losses. We uncover host colonization and virulence factors within a synthetic assemblage of fish pathogens using high-end comparative genomics and address the use of probiotics and paraprobiotics as applicable disease-prevention strategies in fish larval and juvenile rearing. We finally propose guidelines for future microbiome research of presumed relevance to fish larviculture.

Effects of Probiotic Bacteria Bacillus on Growth Performance, Digestive Enzyme Activity, and Hematological Parameters of Asian Sea Bass, Lates calcarifer (Bloch)

This study was conducted to evaluate different doses of two species of Bacillus (Bacillus licheniformis and Bacillus subtilis), on growth parameters, chemical composition of fish, activity of liver, and digestive enzymes of Asian sea bass. During 8 weeks, juvenile Asian sea bass received diets supplemented with 1 × 10³, 1 × 10⁶, and 1 × 10⁹ CFU g^-1 probiotic in addition to a control diet without added microorganisms. At the end of the trial, growth indices (total weight, total length, specific growth rate, total weight gain, food conversion ratio, and condition factor), body composition (crude protein, crude lipid, ash, and dry matter), digestive enzymes (protease, lipase, and amylase), liver enzymes [aspartate aminotransferase (AST), alanine aminotransferase (ALT), alkaline phosphatase (ALP)], immunologic indicators (lysozyme), and hematological parameters [hematocrit (Hct), hemoglobin (Hb), red blood cells (RBCs), white blood cells (WBCs)] were assessed. Asian sea bass receiving diets supplemented with probiotic Bacillus (Bacillus licheniformis and Bacillus subtilis) showed significantly better growth than those fed the basal diet (control). Regarding body composition, total protein levels and dry matter were higher and lipid levels were lower in fish fed the diet containing 1 × 10⁶ CFU g^-1 probiotic compared with the control group (P < 0.05). Digestive enzymes (protease, lipase, and amylase) and hematological parameters (RBC, WBC, and Hb) were all highest in fish fed diet supplemented with 1 × 10⁶ CFU g^-1 probiotic Bacillus. Also, liver enzymes (AST, ALT, ALP) were lower in fish fed diet supplemented with 1 × 10⁶ CFU g^-1 probiotic Bacillus. Being that supplementation of 1 × 10⁶ CFU g^-1 of Bacillus in the diet is the dose which delivers the best results.

The effects of dietary Bacillus cereus QSI-1 on skin mucus proteins profile and immune response in Crucian Carp (Carassius auratus gibelio)

The objective of this study was to investigate the effect of dietary quorum quenching bacterium Bacillus cereus QSI-1 on skin mucus protein pattern and innate immune response in Crucian Carp (Carassius auratus gibelio). The differential proteomes of skin mucus of Crucian Carp were analyzed after administration of Bacillus cereus QSI-1 by isobaric tags for relative and absolute quantitation (iTRAQ) labeling, followed by liquid chromatography-tandem mass spectrometry (LC-MS/MS). A total of 1974 proteins were quantified. Using a 1.5-fold change in expression as a physiological significant benchmark, 264 differentially expressed proteins were reliably quantified by iTRAQ analysis, including 130 up- and 134 down-regulated proteins after dietary Bacillus cereus QSI-1. Some Proteins that were involved in immunity included protein S100, annexin, histone H3, lymphocyte cytosolic protein 1, heat shock protein, L-plastin, keratin 91, etc. Furthermore, fish fed 5 × 10⁸ CFU/g Bacillus cereus QSI-1 supplemented diet showed an increase in alternative complement activity and lysozyme activity but expressed a decrease in superoxide dismutase activity in skin mucus (P < 0.05). However, administration of Bacillus cereus QSI-1 had no significant effects on total immunoglobulin level (P > 0.05). These results demonstrated that dietary administration of Bacillus cereus QSI-1 affects skin mucus protein profile and innate immune response in Crucian Carp, and also can enhance the disease resistance of Crucian Carp against A. hydrophila. This is the first report on proteomics analysis of skin mucus proteins in Crucian Carp after administration of quorum quenching bacterium Bacillus cereus, and the results will help to understand the mucosal immune responses to probiotics at the protein level in fish.

Evaluation of dietary Hybanthus enneaspermus (Linn F. Muell.) as a growth and haemato-immunological modulator in Labeo rohita

This study evaluated the effects of Hybanthus enneaspermus aqueous extract (HEE) as a feed supplement on growth, immune responses, haematological, and biochemical parameters of Labeo rohita and its susceptibility to Aeromonas hydrophila infection. Diets containing five variable concentrations of HEE (g kg^-1) (0 [basal diet], 1.0 [H1], 2.0 [H2], 3.0 [H3], and 4.0 [H4]) were fed to fish (average weight: 17.2 ± 0.21 g) for 6 weeks. Growth parameters, immune parameters, and haemato-biochemical parameters were examined 6 weeks post-feeding. The results showed that growth parameters, such as final weight (39.47 ± 3.1 g) and specific growth rate (1.92 ± 0.2), were significantly higher in the H3 group than in the control. Immunological parameters such as serum lysozyme (24.73 ± 2.16 U mg^-1), phagocytic activity (19.14± 0.26%), and respiratory burst activity (0.307 ± 0.005) were significantly higher in the H3 group, compared with the control. Among the haematological parameters examined, red blood cells, white blood cells, neutrophils, total serum protein, and albumin levels were significantly higher in the H3 group. However, HEE administration had no significant effect on haematocrit, haemoglobin, monocytes, or eosinophils levels. Blood biochemical parameters, including superoxide dismutase and alkaline phosphatase activities, were higher (P < 0.05) in the H3 group than in the control; however, the opposite result was found for aspartate transaminase, alanine transaminase, glucose, and cholesterol. Supplementation with 3 g kg^-1 HEE increased the activities of intestinal digestive enzyme (amylase, protease, and lipase) in fish. Moreover, fish fed diets supplemented with 3 g kg^-1 HEE exhibited the highest disease resistance against A. hydrophila infection. These results suggest that dietary administration of HEE (at 3 g kg^-1) has several positive effects on growth, immune and haematological responses in L. rohita.