Combined and Singular Effects of Dietary PrimaLac® and Potassium Diformate (KDF) on Growth Performance and Some Physiological Parameters of Rainbow Trout (Oncorhynchus mykiss)

Eubiotic Effect of a Dietary Bio-Aqua® and Sodium Diformate (NaDF) on Salmo trutta caspius: Innate Immune System, Biochemical Indices, Antioxidant Defense, and Expression of Immunological and Growth-Related Genes

The present study investigated the effects of combined and singular oral administration of Bio-Aqua® with different dosages of sodium diformate (NaDF) on biochemical indices, innate immune responses, antioxidant effects, and expressions of immunological related genes of Caspian brown trout (Salmo trutta caspius). Fingerlings Salmo trutta caspius (n = 1800; initial weight 15 ± 3 g) were randomly allocated into five groups (120 fish group-1 in triplicates). Control diet: without any addition, G1, G2, G3, and G4 received diets containing 0.2 g kg-1 commercial probiotic Bio-Aqua® combined with 0, 0.5, 1.0, and 1.5% NaDF to the basal diet for 60 days according to recommended dosages reported in previous studies. Results indicated that serum bactericidal activity (G3 on day 60 and G1 on day 30) and classic complement in all groups (on day 60) (G1 and G2 on day 30) were significantly elevated (P < 0.05). The serum lysozyme, glucose, globulin, and albumin levels showed no significant differences between all groups compared to the control group (P > 0.05). On days 30 and 60 of the sampling, no significant difference was observed in the amount of superoxide disotase (SOD) and catalase (CAT) between the treatments (P > 0.05) but activity of malondialdehyde (MDA) was lower in G1 than the control (P < 0.05). The expression of the immune-regulating genes IL-10, IL-1β, GTP, FATP, and IGF was significantly improved in all probiotic + acidifier-treated groups (P < 0.05). The current findings showed that mixture of Bio-Aqua® and NaDF (1.5% + pro) is beneficial, as it effectively improves some immune parameters and expression of immunological and growth-related genes in Caspian brown trout.

Construction of pH-sensitive sodium alginates/sodium carboxymethyl cellulose/zeolite P composite hydrogel microspheres loaded with potassium diformate

As a substitute for feed antibiotics, potassium diformate (KDF) can effectively inhibit bacterial overgrowth in the gastrointestinal tract. To avoid the sudden release of KDF in the stomach, this article proposes a new controlled drug delivery system for controlled drug release. In this system, P-type zeolite molecular sieve (Zeolite P) and drug KDF are combined and embedded into the hydrogel microspheres of sodium alginate (ALG) and sodium carboxymethyl cellulose (CMC). In addition, ALG/CMC/Zeolite P composite hydrogel microspheres were prepared with Ca²⁺ as the crosslinking agent. The structure, composition, morphology, and thermal stability of the hydrogel microspheres were systematically characterized. The effect of the composition ratio of ALG and CMC on the swelling properties of the hydrogel microspheres was also investigated. The results revealed that ALG and CMC form a hydrogen bond and chelate with Ca²⁺ to form a double crosslinked network structure. Thus, Zeolite P can be effectively encapsulated in the hydrogel microspheres to form a dense three-dimensional network structure. Particularly, Zeolite P helps in improving the thermal stability of microspheres, balance the swelling properties, and control the release of KDF. The drug release results and release kinetics reveal that the ALG/CMC/Zeolite P composite hydrogel has higher drug release in an environment with pH 7.4. The release kinetics follow the Ritger-Peppas model and the first-order kinetic model, which indicates that the composite hydrogel has good specific pH sensitivity. In vitro antibacterial experiments revealed that the composite hydrogel microspheres have broad-spectrum antibacterial activity, and certain inhibitory effects on Escherichia coli, Staphylococcus aureus, and Bacillus subtilis.

The Feed Additive Potassium Diformate Prevents Salmonella enterica Serovar Pullorum Infection and Affects Intestinal Flora in Chickens

Extensive studies have shown that potassium diformate (KDF), an antibiotic substitute used as a feed additive, improves animal growth performance, although there is less direct evidence of its preventive effect on bacterial infections and its influence on the intestinal flora of animals. In this study, the inhibition effect of KDF on Salmonella enterica serovar Pullorum, an important enteric pathogen causing pullorum disease, was investigated in vitro and on a chicken infection model. The effect of KDF on the diversities and structures of chicken duodenal and cecum flora were also investigated using 16S rRNA gene sequencing. The results showed that addition of 0.5% KDF in feed or 0.1% KDF in drinking water significantly reduced the bacterial loads and the degree of pathological changes in the cecum, improved digestion and reduced the pH of the gastrointestinal tract of chickens infected with S. pullorum. KDF also significantly modified the diversity and abundance of intestinal microflorae in chickens. In particular, it promoted the colonization of several probiotics, such as Bacteroides, Blautia, Ruminococcus_torques_group and Faecalibacteriumm, which are involved in maintenance of the intestinal barrier, modulation of inflammation, energy supply for intestinal cells and pathogen resistance. These results enrich the theoretical basis for the clinical application of KDF in chickens.

Single and Multi-Strain Probiotics Supplementation in Commercially Prominent Finfish Aquaculture: Review of the Current Knowledge

The Nile tilapia Oreochromis niloticus, Atlantic salmon Salmo salar, rainbow trout Oncorhynchus mykiss, olive flounder Paralichthys olivaceus, common carp Cyprinus carpio, grass carp Ctenopharyngodon idella and rohu carp Labeo rohita are farmed commercially worldwide. Production of these important finfishes is rapidly expanding, and intensive culture practices can lead to stress in fish, often reducing resistance to infectious diseases. Antibiotics and other drugs are routinely used for the treatment of diseases and sometimes applied preventatively to combat microbial pathogens. This strategy is responsible for the emergence and spread of antimicrobial resistance, mass killing of environmental/beneficial bacteria, and residual effects in humans. As an alternative, the administration of probiotics has gained acceptance for disease control in aquaculture. Probiotics have been found to improve growth, feed utilization, immunological status, disease resistance, and to promote transcriptomic profiles and internal microbial balance of host organisms. The present review discusses the effects of single and multi-strain probiotics on growth, immunity, heamato-biochemical parameters, and disease resistance of the above-mentioned finfishes. The application and outcome of probiotics in the field or open pond system, gaps in existing knowledge, and issues worthy of further research are also highlighted.

Assessing the Influence of Dietary Pediococcus acidilactici Probiotic Supplementation in the Feed of European Sea Bass (Dicentrarchus labrax L.) (Linnaeus, 1758) on Farm Water Quality, Growth, Feed Utilization, Survival Rate, Body Composition, Blood Biochemical Parameters, and Intestinal Histology

The probiotics are being used as ecofriendly and bioremediation tools for developing sustainability to aquaculture. The present study was conducted to explore the practical capability of using dietary lactic acid bacteria (Pediococcus acidilactici) probiotics and see how its dose variation affected the water quality, growth performance, survival rate, body composition, blood biochemical parameters, and intestinal histology of European sea bass (Dicentrarchus labrax L.). A total of 120 fingerlings with an initial weight of $9\pm 0.2$  g were divided into four groups, each with three replicates. The feeding experiment lasted for 60 days. In addition to the control (without probiotics) (T0), fish were fed diets containing (T1) 2.0, (T2) 2.5, and (T3) 3.0 g of probiotics per kg of diet twice a day. When compared to the control, sea bass fed probiotic-supplemented diets had significantly higher growth parameters, fish body “crude lipid,” and villi height ( $p<0.05$ , $p<0.01$ , and $p<0.001$ ). The P. acidilactici probiotic treatments improved survival rate, feed conversion ratio, body composition, and blood biochemical markers, but not statistically significant ( $p>0.05$ ). Also, in regard to water quality, P. acidilactici drastically reduced ammonia and pH levels. In this experiment, fish fed with a dosage of 3.0 g of this commercial probiotic per kg of probiotics performed better. The study found that including probiotics in the diets of European sea bass improved growth, body composition, survival rate, blood biochemical markers, intestinal histology, and some water quality parameters.

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.