Search

With increasing intensive aquaculture production, the search for nourishing, environmentally, and economically viable fishmeal (FM) alternative is an endless approach. Therefore, the present study examines the effect of the use of black soldier fly, Hermetia illucens, larvae meal (BSFM) as an alternative protein for FM in the diet of Nile tilapia, Oreochromis niloticus, on nitrogen wastes, zootechnical performance, body composition, and hematobiochemical parameters. A total of 315 Nile tilapia fingerlings (4.11±0.12 g/fish) were divided into seven treatments in triplicate. The fish were stocked in glass aquaria (50 × 40 × 30 cm; 60 L each) at a rate of 15 fish per aquarium. Experimental diets contained BSFM at increasing levels of 0, 5, 10, 15, 20, 25, and 30% as FM replacers were offered twice daily to apparent satiation for 84 days. The results revealed that BSFM replacements significantly (P = 0.001) enhance water quality and reduce the total ammonia, NH3, and NO2levels compared to the control. The growth performance, feed conversion ratio, and survival were improved with increasing BSFM meal inclusion levels up to 25% (P = 0.001, 0.017, and 0.001, respectively). However, the zootechnical performance of the experimental fish started to decline with increasing replacement levels to 30%. Also, by an increase in BSFM level to 25%, hematobiochemical markers were considerably (P≤0.01) enhanced. The liver and kidney function indicators improved (P = 0.001) with dietary BSFM. The economic evaluation revealed that feed costs and fish weight gain were decreased by increasing BSFM levels in fish diets. The current study highlighted the potential environmentally beneficial use of BSFM as an FM replacer in terms of reducing water nitrogen waste levels and improving growth performance, health status, and enhancing the economic feasibility of the commercial tilapia diet.

To sustain normal development, high survival, and rapid growth, marine fish larvae require a diet rich in polyunsaturated fatty acids, which could decrease the risk of reactive oxygen species accumulations. Consequently, a 60-day feeding experiment was conducted to determine the effect of silymarin (SM) supplementation in weaning diets on the growth performance, survival, antioxidant enzyme activities, and fatty acids profile of European seabass (Dicentrarchus labrax) larvae. Four isonitrogenous and isolipidic diets were investigated using SM at levels of 0, 200, 400, and 600 mg kg−1(SM0.00, SM200, SM400, and SM600, respectively). The findings showed that, in a dose-dependent manner, increasing dietary levels of SM enhanced survival, growth, and feed utilization. In the SM600group, the weight gain, survival, and feed conversion ratio (FCR) improved by 123.21, 11.66, and 38.72%, respectively, compared to the control group. The dose-response analysis demonstrated a strong positive correlation (R2=0.96) between SM levels and weight increase, and a strong negative correlation (R2=0.88) between SM levels and FCR. The antioxidant enzyme activities of larvae given SM-enriched diets were significantly greater than those of the control group. Compared to the control group, the CAT and SOD improved by 81.77 and 5.08% in the SM600 group. In addition, the saturated fatty acid content decreased while the unsaturated fatty acid content increased, particularly in the SM600 group. The results indicate that supplementing the micro diet of European seabass larvae during weaning with SM at a dose of 600 mg kg−1increases growth, survival, antioxidant status, and fatty acid profiles.

The present study aimed to identify the carotenoid content and evaluate the antioxidant activities of spirulina, Arthrospira platensis(in vitro), and the effect of its supplementation to a vegetarian diet on growth performance, feed utilization, body proximate composition and physiological status of Nile tilapia, Oreochromis niloticus(in vivo). The carotenoid content of spirulina was identified by UPLC-MS/MS and showed that transand cisβ-carotene were the major carotenoids (88.3%) followed by β-cryptoxanthin and zeaxanthin. The antioxidant activity of spirulina was determined in water and crude carotenoid extracts by 2,2-diphenyl-1-picryhydrazyl (DPPH) scavenging assay, both extracts showed a significant free radical scavenging capacity. In addition, Nile tilapia fry (0.83 ± 0.01 g) was fed a vegetarian diet supplemented with different levels of spirulina for 12 weeks. The results revealed that the highest growth performance and nutrient utilization were recorded with 0.5% spirulina and the peak response determined at 0.63%-0.65% using polynomial second order regression. Also, the hemoglobin content improved in a quadratic regression model with the peak at 0.67% spirulina. Plasma total protein and lipid contents increased significantly with spirulina levels over 0.50%. Moreover, the aminopeptidase activities and glucose level decreased significantly with increasing spirulina levels. The current study recommended the supplementation of the Nile tilapia vegetarian diet with spirulina at levels of 0.63-0.65% for better growth performance and physiological status.

The study herein evaluated the effects of dietary supplementation with different yucca (Yucca schidigera) extract levels on rearing water quality, growth performance, protein utilization, hematological and immunological status, and economic benefits of cultured European seabass (Dicentrarchus labrax) juveniles. Yucca extract (YE) was incorporated in an experimental diet at levels of 0, 0.25, 0.50, and 1 g YE kg−1, and offered to fish reared in 70-L glass aquaria (15 fish per aquarium; three replicates each). Dietary YE supplementation significantly (P<0.05) decreased ammonia-nitrogen levels in water. Compared with the control, groups fed 0.50 and 1 g YE kg−1diets showed improved growth performance (by 26.02% and 36.98%, respectively) and protein efficiency ratio (by 31.39% and 37.29%, respectively). In addition, hematological parameters (red blood cells, hemoglobin, hematocrit, white blood cells and neutrophil) and innate immune parameters (globulin fractions and lysozyme activity) improved with increasing dietary YE levels. Growth, hematological, and immunological parameters increased with a polynomial second-order regression models, with curves peak close to 1 g YE kg−1diet. The cortisol level decreased significantly (P<0.05) with increasing dietary YE levels. The groups fed the 0.50 and 1 g YE kg−1diets generated significantly (P<0.05) higher revenue than groups fed the 0.25 g YE kg−1and the control diets. The using of YE is recommended as a dietary feed additive at a level of 1 g kg−1for reducing the environmental footprint of fish protein production, accelerating growth, and improving health status of cultured seabass in a short-term feeding period.

The aim of the present study was to evaluate the efficiency of natural zeolite (Z) and Yucca schidigeraextract (YE) as water treatments for European seabass, Dicentrarchus labrax, reared at high stocking density. A factorial design was conducted using two socking densities (100 and 200 fingerlings/m3) and five water treatments (control, zeolite 10 g/L, zeolite 15 g/L, YE 0.75 ml/l, and YE 1 ml/L). The fish (with an initial weight of 5.83 g) were allocated into 1 m3fiberglass tanks in triplicates per each treatment and fed a commercial diet for 45 days. The results demonstrated that rearing European seabass at a high stocking density (200 fish/m3) caused a significant deterioration in water quality parameters, such as dissolved oxygen, NH3-N, NH4-N, NO2-N, and NO3-N by 11.11 %, 49.5 %, 33.33 %, 38.46 %, and 9.09 %, respectively compared to the low stoking density. Furthermore, increasing the stocking density of European seabass significantly reduced growth performance, feed utilization, and various haemato-biochemical parameters. The water treatment with both zeolite and YE significantly improved dissolved oxygen levels and decreased the nitrogen derivatives in tanks water of low and high stocking densities. Also, the water treatments ameliorated the effects of increasing stocking density on fish growth performance, feed utilization, hematological, and biochemical parameters. Whereas the highest wight gain (32.17 g), survival (93 %), and best FCR (1.9) were recorded in group treated with high zeolite level at low stocking density. Regarding the efficiency of both water treatment materials used in this study, water treatment with zeolite at the highest level (15 g/L) outperformed YE in different evaluated parameters of water quality, fish growth, and physiological performance. The mean effects of zeolite and YE at high levels showed an improvement of weight gain and feed conversion ratio by 103.68 %, 46.37 %, 30.90 %, and 23.47 %, respectively, compared to the control. Moreover, the effects of each substrate were level dependent. In conclusion, the water treatment with zeolite and YE could improve the wellbeing and production of seabass fish in favor of zeolite (15 g/l).

•Aqueous exposure to low levels of silver nanoparticles (Ag-NPs) has been evaluated.•The 10 µg L-1 Ag-NPs improved growth performance and health status of Nile tilapia.•The 10 µg L-1 Ag-NPs alleviated the histopathological changes induced by Aeromonas hydrophila challenge.•Increasing Ag-NPs concentration decreased total bacterial count in the fish rearing water.•Higher concentrations of Ag-NPs than 30 µg L-1 could have potentially toxic effects on Nile tilapia.

•The effect of palaemon and artemia dried biomass on reproductive performance of D. labraxhas been studied•The egg quality improved with crusteacean supplementation.•The fecundity, viability, fertilization and hatching (%) improved with crusteacean supplementation.•Palaemon and artemia are cheap potential feed ingredient in the diet of D. labraxbroodstock for improving reproductive.