Effects of Stocking Density on Growth Performance and Stress Responses of Bester and Bester ♀ × Beluga ♂ Juveniles in Recirculating Aquaculture Systems

Effects of Dietary Agavin on the Gut Microbiota of the Nile Tilapia (Oreochromis niloticus) Reared at High Densities

High-density stress can lead to dysbiotic microbiota, affecting the organism's metabolic, and protective functions. Agavin is a fructan with prebiotic properties that regulate the gut microbiota by promoting the growth of beneficial bacteria. This study evaluated the effect of agavin on the gut microbiota using Next-Generation Sequencing (NGS) and its correlation with the growth parameters. Four groups of fish were fed different diets: a control diet (negative and positive control), without agavin supplementation, and two experimental diets supplemented with agavin at 20 g kg-1 and 40 g kg-1. Nile tilapias (1.04 g ± 0.01 g) were fed for 110 days. After 90 days of feeding, fish were subjected to high-density stress (63 kg m-3) for 20 days, except for the negative control. NGS detected 1579 different operational taxonomic units in the samples. In the correlation analysis of growth parameters, the families Vibrionaceae and Methyloligillaceae showed a positive correlation with fish growth parameters, these results may serve to know the relation of agavin and microbiota on the growth performance, as well as the metabolic activities of families in tilapia. Furthermore, high-density stress and agavin supplementation modify the gut microbiota in tilapia. At a low-density, supplementation with 20 g kg-1 agavin promoted the growth of the potentially beneficial families Sphingomonadaceae, Oxalobacteriaceae, and Chitinophagaceae; at high densities, reduced the abundance of pathogenic families (Vibrionaceae and Aeromonadaceae). These results suggest that, under stress conditions, agavin can stimulate the growth of potentially beneficial bacteria and reduce the growth of potentially pathogenic bacteria, suggesting its potential use as a prebiotic in aquaculture.

Modulation of growth performance, feed utilization, and physiological traits in redbelly Tilapia (Tilapia zillii) through environmental and sex-based interactions

This study explored the combined influence of tank color, stocking density, and gender on Tilapia zillii's performance and well-being. In this 120-day trial, 320 T. zillii, each initially weighing 10.0 ± 0.1 g/fish, were distributed among 24 tanks. The experiment included eight distinct treatment combinations, varying tank color (blue and green), stocking density (10 and 30 fish/m3) and sex (monosexual and mixed). The results showed that blue tanks improved specific growth rate and condition factor, while green tanks were better for feed utilization. Density at 30 fish/m3 showed the highest mean values of final body weight and total length, weight gain (WG), and gain length. Mono-sex outperformed mixed-sex ones in WG and daily growth. Interactions between color, density and sex were significant, affecting growth and feed utilization. Green tanks were best for protein profiles, while blue tanks excelled in glucose. A density of 10 fish/m3 yielded the highest protein profiles, and mono-sex fish had higher protein profiles. For lipid profiles, green tanks were superior, and density affected lipid profiles. Mixed-sex populations were best for certain lipid profile parameters. Interactions between these factors also played a significant role, making the biochemical profiles of T. zillii a complex interplay of various factors. The results explored that tank color, fish density and sex influence the activity of nonspecific immune enzymes in the liver of T. zillii. Blue tanks and lower fish density led to higher nonspecific immune enzymes, while mono-sex fish exhibited more significant nonspecific immune enzymes. Complex interactions between these factors also influenced nonspecific immune enzyme activities. Blue tanks increased malondialdehyde (MDA) levels, while green tanks raised glutathione S-transferases (GST) and catalase (CAT) levels. Lower fish density led to higher MDA, while higher density increased GST and CAT. Mono-sex fish had more MDA and GST, while mixed-sex fish showed greater CAT levels. Complex interactions among these factors affected the antioxidant levels in T. zillii. In summary, our study suggests that rearing T. zillii in green tanks at higher densities (30 fish/m3) and in mono-sex conditions yields the best results in terms of growth and overall performance.

The Antioxidant and Hepatoprotective Potential of Berberine and Silymarin on Acetaminophen Induced Toxicity in Cyprinus carpio L

Berberine (BBR) and silymarin (SM) are natural compounds extracted from plants known for their antioxidant and chemoprotective effects on the liver. The present study aimed to investigate the beneficial properties of BBR and SM and the association of BBR with SM on liver function using fish as "in vivo" models. Moreover, the study investigated their hepatoprotective role after acetaminophen (APAP) exposure. For this purpose, the fish (N = 360; 118.4 ± 11.09 g) were fed with control or experimental diets for 9 weeks. In the experimental diets, the feed was supplemented with either SM (1 g/kg feed), BBR (100 and 200 mg/kg feed), or a combination of BBR with SM (SM 1 g/kg feed + BBR 100 mg/kg feed and, respectively, SM 1 g/kg feed + BBR 200 mg/kg feed). After the feeding trial, seven fish from each tank were randomly selected and exposed to a single APAP dose. The selected serum biochemical markers, oxidative stress markers, and lysozyme activity were used to evaluate the efficiency of the supplements on carp's health profile, particularly regarding the hepatopancreas function. Our results showed that the inclusion of SM and BBR (either as a single or in combination) reduced the serum contents of total cholesterol, triglyceride, and alanine transaminase. An increase in the high-density cholesterol was observed after the administration of BBR or BBR in association with SM. Both supplements showed hepatoprotective activity against APAP-induced hepatotoxicity, especially BBR. The ameliorative effects of SM (1 g) in association with BBR (100 mg) were highlighted by the modulation of the nonspecific immune system and oxidative stress alleviation after APAP exposure.

Influence of salinity on the biometric traits of striped catfish (Pangasianodon hypophthalmus) and barley (Hordeum vulgare) cultivated under an integrated aquaculture-agriculture system

BACKGROUND

Soil salinity, soil infertility, and freshwater scarcity are among the major constraints affecting agricultural ecosystems in arid and semi-arid regions of the world. Hence, there is a need to look for salt-tolerant crops and fish that can be successfully cultivated and reared respectively in such harsh environments. The implementation of biosaline integrated aquaculture-agriculture systems (IAAS) utilizing both salt-tolerant crops and fish could improve food and feed production in arid and semi-arid regions. This study, therefore, investigated the influence of salinity on the biometric traits of striped catfish (Pangasianodon hypophthalmus) and barley (Hordeum vulgare) under an IAAS.

METHOD

The experiment followed a randomized completely block design of three salinity treatments with three replicates namely, T0: Control (freshwater mixed with chemical fertilizers), T1: 5,000 ppm, T2: 10,000 ppm, and T3: 15,000 ppm.

RESULTS

Irrigating barley with saline aquaculture wastewater at different salinities (5,000 ppm, 10,000 ppm, and 15,000 ppm) did not significantly affect the agro-morphological parameters (internode number per plant, stalk diameter, leaf number per plant, leaf area index, and leaf chlorophyll content (SPAD)) of the plants at 90 days after sowing. Moreover, the forage yield and forage quality in terms of fiber fraction, nutrient composition, and in vitro digestibility of the forage biomass were not severely affected by high salinity compared to the control (freshwater and inorganic fertilizers). Our results also showed that rearing striped catfish in saline water not exceeding 10,000 ppm did not negatively impact the growth performance (final weight, body weight gain, feed conversion ratio, specific growth rate, condition factor, and survival) and the health status of the fish.

CONCLUSIONS

The integration of striped catfish and barley production in water salinities below 15,000 ppm could be a feasible alternative in safeguarding food and feed security in regions affected by soil salinity, soil infertility, and freshwater scarcity. Moreover, the salinity regime of 5,000 ppm could bring higher economic gains to farmers regarding higher crop yields (fish and forage yield).

Evaluation of DDGS as a Low-Cost Feed Ingredient for Common Carp (Cyprinus carpio Linneus) Cultivated in a Semi-Intensive System

Distillers dried grains with solubles (DDGS), a coproduct from the ethanol production industry, is successfully used as an ingredient in feeding cattle and pigs due to its relatively high protein and nutrient content and low price compared to cereals. The aim of this study was to establish the optimal DDGS concentration that can be included in the diet of common carp. A seven-week experiment was performed on common carp with an initial weight of 86 g feed with three experimental diets D0 (DDGS 0%), D1 (DDGS 25%) and D2 (DDGS 35%). The chemical composition of DDGS analyzed by Fourier Transform Near-Infrared (FT-NIR) spectroscopy showed a protein content of 27.56% and oil at 6.75%. Diets with DDGS did not produce significant changes in growth parameters, flesh quality, and blood biochemical profile. Regarding the oxidative status in the muscle tissue, D1 and D2 significantly reduced, in a dose-dependent manner, the specific activity of SOD and GSH, while CAT and GPX were left unaffected. In the liver tissue, CAT, GSH, MDA and carbonylated proteins were reduced in the DDGS diets. The microbiological analysis of the intestinal contents revealed a variation in microbial density depending on the diet used. The total number of aerobic germs was between 224.2 × 104 and 69.84 × 106 (D2 > D1 > D0) and the total number of anaerobic germs was between 15.2 × 102 and 28.2 × 102 (D2 > D0 > D1).

Infection and antibiotic treatment have prolonged effect on gut microbiota, muscle and hepatic fatty acids in rainbow trout (Oncorhynchus mykiss)

AIMS

The aim of the present study was to investigate the gastrointestinal (GI) microbiota and bacterium-specific fatty acid occurrence in the muscle and hepatic lipids of rainbow trout Oncorhynchus mykiss (Walbaum, 1792), both healthy and those naturally infected with bacterial pathogens.

METHODS AND RESULTS

From June 2017 (L1) to September 2018 (L8), 74 specimens of rainbow trout Oncorhynchus mykiss (with the average weight from 139.2 ± 7.1 g (L1) to 2191.7 ± 85.1 g (L8)) were studied. Amplicon sequencing targeted to the V3-V4 region of 16S rRNA gene fragments is used for identification of taxonomic composition of gut bacterial communities. Firmicutes, Bacteroidetes, Proteobacteria, Tenericutes, and Fusobacteria were the major phyla. Besides behavioural and physiological manifestations of the bacterial mixed disease (yersiniosis, pseudomonosis, and flavobacteriosis), some disorders induced both the infection and followed antibiotic treatment were detected in the host organism, including (1) a progressive decrease in the content of odd-chain saturated fatty acids of bacterial origin within the trout lipid molecules and (2) abnormalities in trout GI tract microbiota, such as the elimination of LAB and progressive occurrence of certain bacterial taxa, particularly Mycoplasmataceae.

CONCLUSIONS

The GI bacterial flora varied principally due to Mycoplasmataceae and Lactobacillaceae, which could be considered in the search for bioindicators. The content of specific bacterium-derived fatty acids incorporated into the lipids of trout muscle and hepatic seems to be related to the prevalence of bacterial taxa, and their deficit could be regarded as an early warning sign of microbiota disturbance.

SIGNIFICANCE AND IMPACT OF STUDY

Our results demonstrated that infectious disease and antibiotic treatment of reared species can cause pertinent imbalance in their gut microbiota and reduce the abundance of specific fatty acids. This can be useful for the sustainable aquaculture industry due to development of early indication technologies for rapid disease diagnosis.

Wheat and Barley Grass Juice Addition to a Plant-Based Feed Improved Growth and Flesh Quality of Common Carp (Cyprinus carpio)

Simple Summary

Several plant extract additives are being increasingly used in aquaculture for their positive effects on fish growth and immunity. Plant extract additives are called phytogenics. The chemical composition of the additives influences their biological activity. The plant extracts used in this study were wheat grass juice and barley grass juice. Their inclusion in a plant-based diet for common carp improved growth performance and flesh quality. The positive effects of the plant extracts could be attributed to their contents of unsaturated fatty acids, essential amino acids, sugars and organic acids.

Abstract

Phytogenics are plant extract additives used for their bioactive properties. The objective of this study was to assess the effect of plant extracts, wheat grass juice (WGJ) and barley grass juices (BGJ) addition to fish diet on growth and meat quality of common carp. Fish (51 ± 33 g initial weight) were fed for four weeks with three plant-based diets: (1) control feed (Con), (2) control feed supplemented with 2% WGJ (Con+WGJ), and (3) control feed supplemented with 2% BGJ (Con+BGJ). The results showed that the inclusion of the two juices in the plant-based feed stimulated the growth and improved meat quality by lowering the fat and ash content. Feed conversion ratio and condition factor were not affected. There were no significant differences in Fe and Zn contents of meat; however, Cu decreased, while Mn was lower in the Con+WGJ group and higher in the Con+BGJ group compared to Con. A high content of unsaturated fatty acids (FA, oleic acid and linoleic acid) and desirable ratios of saturated/unsaturated FA (0.27–0.29) and Ω6/Ω3 (2.5–2.78) were found in all groups. The juices were characterized in terms of lipid profile and polar compounds by GC-MS technique. The observed positive effects can be attributed to the rich composition of juices that included unsaturated FA, amino acids, sugars and organic compounds.