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A 60-day experiment was performed to assess the efficacy of dietary Astragalus membranaceus polysaccharides (ASP) in attenuation of sub-lethal thallium (Tl) toxicity in Nile tilapia. Six experimental groups (in triplicates) were designed where a fish group was raised in clean water and fed basal diet and served as control (CONT), two groups were fed the basal diet supplemented with 0.15% and 0.30% ASP (ASPL and ASPH), Tl-intoxicated group exposed to 1/10 of 96-h LC50 (= 41.9 μg/L), and two other groups were fed 0.15% and 0.30% ASP and concomitantly exposed to 41.9 μg Tl/L (ASPL-Tl and ASPH-Tl). At the end of the experiment, fish behavioral responses, clinical signs, survivability, growth, whole-body composition, intestinal digestive enzymes, serum biochemical parameters, hepatic antioxidative biomarkers, and transcription of stress and apoptosis genes were assessed. Results showed that the whole-body composition, intestinal α-amylase and protease enzymes, serum AST and blood urea levels, and hepatic GSH were not significantly different among groups (P 0.05). The Tl-intoxicated fish group was off food, had darkened skin, showed restlessness and hyperexcitability, and high mortalities. FBW, WG, SGR and FI were significantly decreased alongside increase FCR in the Tl-exposed group. Tl exposure caused significant increases (P 0.05) in intestinal lipase enzyme and serum indices such as ALT, creatinine, total cholesterol, triglycerides, glucose, and cortisol levels. Moreover, a significant decreases in hepatic CAT and SOD enzyme activities and significant increases in hepatic MDA contents were also noticed (P 0.05). Furthermore, Tl exposure induced significant upregulation of hepatic HSP70 and apoptosis-related genes (p53 and caspase 3). Interestingly, dietary supplementation with ASP in ASPL-Tl and ASPH-Tl groups modulated the parameters mentioned above but still not reached the CONT values. Altogether, this study suggests that ASP could be beneficial in the modulation of sub-lethal Tl toxicity effects in Nile tilapia. Additionally, we can conclude that using natural feed supplements such as ASP in aquafeed might be necessary for maintaining the overall health performances of Nile tilapia.

An 84-day feeding trial was performed to investigate the effects of dietary curcumin (CUR) supplementation on growth performance, feed utilization, immunity, antioxidant response, and resistance to Aeromonas hydrophila in Oreochromis niloticus . Three hundred tilapia fish (average initial weight; 2.55 ± 0.003 g) were fed five diets supplemented with 0 (basal diet), 50, 100, 150 or 200 mg CUR kg − 1 diet. Herein, a concentration-dependent inhibition of both A. hydrophila and A. sobria following in vitro CUR treatment was evident. The in vivo results revealed that CUR supplementation at different levels, especially at 50 mg kg − 1 diet, evoked significantly higher final weight, daily weight gain, and specific growth rate in tilapia. Also, CUR100 and CUR150 fish groups had the best feed conversion and protein efficiency ratios. Also, a significant increase in both crude lipid and protein content of the whole body was recorded in fish fed 50 or 100 mg CUR kg − 1 diet. A significant increase of both catalase activity and reduced glutathione content with a significant incline in the MDA level were recorded with dietary CUR supplementation. Lysozyme activity, total IgG and IgM levels significantly increased, especially in fish fed the 50 mg CUR kg − 1 diet. A concentration-dependent decline in the total bacteria, Coliforms, Escherichia coli and Aeromonas spp. counts was recorded in water samples and intestinal content of tilapia with CUR addition. High survival rate was obvious in all CUR supplemented groups after challenge with A . hydrophila . It is concluded that CUR could be a candidate dietary supplement in fish improving growth performance, feed utilization, oxidative status, immune responses, and disease resistance.

The present study was conducted to investigate the toxic effect of abamectin (ABM) and to evaluate the modulatory role of heat treated jojoba leaves extract (JLE) as feed additive in Oreochromis niloticus (O. niloticus) fish. 300 Nile tilapia fingerlings were randomly distributed in to 5 equal groups (4 replicates each). The first group (control) was fed on basal diet. The second group (ABM) was fed on basal diet and exposed to 1/10 of the 96 h LC50 of ABM (20.73 μg/L). The third (ABM + JLE0.5), the fourth (ABM + JLE1) and the fifth (ABM + JLE2) groups were exposed to ABM and fed on diet supplemented with 0.5, 1 and 2 g JLE/kg, respectively. ABM altered the water quality parameters by increasing the total ammonia and reducing the dissolved oxygen while JLE reversed these effects. Apart from feed conversion, ABM decreased the growth parameters of exposed fish when compared to control. These values were modulated in JLE exposed groups in a concentration dependent manner. ABM increased ALT and AST levels while JLE1 and JLE0.5 restored their levels to the control values, respectively. ABM altered the lipid profile of exposed fish while JLE2 restored total cholesterol to normal value. Reduced glutathione content was decreased by ABM and was restored to normal by JLE2. The highest level of lipid peroxidation (MDA) was recorded in ABM and ABM + JLE0.5 groups while JLE1 and JLE2 decreased the MDA level. The total antioxidant capacity was decreased by ABM while the highest value was recoded in both control and JLE0.5 groups. The level of IgG, IgA and C3 were decreased by ABM while its level was restored to normal by using JLE. Exposure of fish to ABM resulted in a significant increase in the nitric oxide level. ABM group had lower moisture and higher crude lipids in the whole-fish body than the supplemented groups. It could be concluded that dietary supplementation of JLE can positively attenuate the toxic effects of ABM on growth, immunity, physiological and antioxidant parameters thereby improving the general health condition and decreasing the mortality of O. niloticus. Additionally, the heat treatment attempted on the leaves could be considered as an eco-friendly method for detoxification.

The current study was conducted to investigate the stress effect of high stocking density and to evaluate the efficiency of Glycyrrhiza glabra extract (LE) and protexin concentrate (PC) in Oreochromis niloticus. A total of 360 Nile tilapia fingerlings were divided into 5 groups. The 1st and the 2nd groups were stocked at a rate of 10 fish/aquarium (control) and 20 fish/aquarium (HSD), respectively. The 3rd group (20 fish/aquarium fed on basal diet supplemented with 200 mg/kg protexin) (HSD + PC). The 4th group (20 fish/aquarium fed on basal diet supplemented with 500 mg/kg LE) (HSD + LE). The 5th group (20 fish/aquarium fed on basal diet supplemented with 200 mg/kg PC+ 500 mg/kg LE) (HSD + PC + LE). HSD group had the lowest body weight, specific growth rate and feed intake. After the Aeromonas hydrophila challenge, fishes from HSD recorded the highest mortality, while the opposite occurred in supplemented groups. It could be concluded that supplementation of LE, PC separately or in combination can positively attenuate the undesirable effects of HSD on growth, antioxidant, immunity and bacterial disease resistance of fish.