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Zinc (Zn) and vitamin E (VE) are essential micro-nutrients that contribute a pivotal role in the physiology and nutrition of fish. An experiment was designed to know the effects of Zn and VE addition in the diet on growth and feed utilization in Nile tilapia (Oreochromis niloticus). Four diets containing Zn (80 mg/kg), VE (50 mg/kg), Zn (80 mg/kg) + VE (50 mg/kg), and without Zn and VE (control) were fed to Nile tilapia in aquaria with triplicate groups for 6 weeks. Survival, growth parameters (weight gain, WG; %WG; specific growth rate, SGR), and feed utilization (protein efficiency ratio, PER; feed conversion ratio, FCR) were calculated at the end of the feeding trial. Several hemato-biochemical parameters (hemoglobin, Hb; red blood cell, RBC; white blood cell, WBC, and glucose) and morphology of muscle were analyzed. The growth parameters (WG, %WG, and SGR) and feed utilization (FCR and PER) improved significantly in the fish fed with Zn, VE, and Zn + VE supplemented diets. There was no significant change in the values of Hb, RBC, WBC, and glucose level among different groups. Significantly improved diameter of muscle fiber, reduced distance between muscle fiber, and increased number of the nucleus and hyperplastic muscle fiber were observed in the fish fed with Zn, VE, and Zn + VE supplemented diets. These results suggested that Zn and VE can be effectively incorporated into the diets of Nile tilapia for better growth with maximum feed utilization.

Heavy metal pollution due to anthropogenic activities poses a great threat to aquatic organisms. The present study was conducted to evaluate the cytotoxic and genotoxic effects of hexavalent chromium (potassium dichromate) on hemato-biochemical, histo-pathological, and genetical changes in striped catfish Pangasianodon hypophthalmus. Three sub-lethal doses (0.8, 1.6, and 3.2 mg/L) of chromium (Cr) were selected and fish were exposed in vivo contrasting with a control (0 mg/L) for 30 days. The study revealed that various hemato-biochemical parameters showed a significant decrease in hemoglobin (Hb), red blood cells (RBCs), and blood glucose content, whereas white blood cells (WBCs) significantly increased in Cr exposed fish. Frequencies of all forms of structural abnormalities of erythrocytes (erythrocytic cellular abnormalities; ECA, erythrocytic nuclear abnormalities; ENA and erythroblasts; Ebs) were significantly increased in higher two test concentrations (1.6 and 3.2 mg/L) when compared to control. Differential leucocyte count exhibited significant increase in neutrophil and decrease in lymphocytes in the highest Cr treated group. The severity of various histo-pathological changes in the gills, liver, and kidney were increased considerably with the increase of Cr concentrations. Similarly, the amount of DNA (ng/μl) decreased significantly in blood and tissues of different vital organs where the liver showed the highest decline compared to control in a concentration-dependent manner. Taken altogether, P. hypophthalmus is susceptible to Cr and can be used as a bio-indicator to assess aquatic metal pollution.

The efficacy and suitability of dietary whole wheat flour supplementation was evaluated on the growth performance and survival of rohu (Labeo rohita). The study was conducted in 12 experimental aquaria at the Wet Laboratory, Department of Aquaculture, Bangladesh Agricultural University, Mymensingh. A total of 180 fingerlings of mean initial weight of 1.744±00 g were stocked at the same stocking density (268 fingerlings/m3). Four different treatments (T1, T2, T3 and T4) each with three replications were performed having different level of whole wheat flour such as 0% whole wheat flour (T1), 5% whole wheat flour (T2), 10% whole wheat flour (T3) and 15% whole wheat flour (T4). Feeds were supplied at 5% body weight twice daily in the morning at 9.00 am and in the afternoon at 5.00 pm throughout the study period. The rations were adjusted every week when new weights of the fish for various experimental aquariums were determined. At the end of the 63 days study period, the growth performance parameters such as mean final weight (g), weight gain (g), percent weight gain (%), specific growth rate (%/day) and the best feed utilization in terms of food conversion ratio were found highest at treatment 4 where fishes were fed with inclusion of 15% whole wheat flour and lowest was found at treatment 1 (fed with inclusion of 0% whole wheat flour). Water quality parameters were within the acceptable range and survival rate was found 100% in all treatment. Therefore, it can be concluded that treatment 4 (highest growth performance and survival rate of L. rohita with supplementation of 15% whole wheat flour containing diet) can be chosen by fish farmers for commercial culture of this species. Res. Agric., Livest. Fish.6(2): 345-352, August 2019

The use of nanotechnology in food production systems is being investigated globally, though there is limited research on its effect on fish nutrition. Therefore, this study aimed to identify the effects of silica nanoparticles (NPs) on the nutrition and physiology of tilapia, Oreochromis niloticus. Four isonitrogenous diets (300 g/kg crude protein) with NPs (0, 1, 2, and 3 mg/kg diet) were fed to fish (6.52 ± 0.20 g) in a recirculatory aquaculture system for 56 days. Throughout the study period, the effects of silica NP on survival rate, blood cell count, hemoglobin (Hb) level, condition factor (CF), and final product composition (except lipid content) were insignificant. However, growth performance and feed efficiency increased with an increasing level of silica NP, up to 2 mg/kg, and then decreased. This increase was due to the highest apparent protein digestibility and dry matter digestibility when fish were fed silica NP at 2 mg/kg. However, fish at the early stage showed better performance in all dietary groups than in later. Blood glucose (BG) content and histology of the kidney revealed that fish were stressed when a 3 mg/kg silica NP was used and they adapted through excessive excretion via expanded glomeruli. Though no significant effect on villi length was observed, silica NP increased the surface area widening the villi of the gut along with the number of goblet cells in the intestine significantly, when supplemented at a level of 2 mg/kg. The bioaccumulation of silica shows that incorporating silica NP in the fish feed will not compromise human health safety upon consumption. Although silica NP at 1 mg/kg and 3 mg/kg yielded some improvements to growth and final product quality, a 2 mg/kg silica NP generated the best results in all measured parameters.

The analytical experiment was executed to present detailed reports on the concentration of heavy metals (nickel, iron, zinc, manganese, chromium, lead, and cadmium) in farmed shrimp, Penaeus monodon and its concomitant human health risks upon consumption. A total of 147 farms from six sub-districts of Khulna were selected for sample collection and concentration of heavy metals were determined by Atomic Absorption Spectrometry (AAS) method, following electro-thermal heater digestion. Ni and Cr were found considerably below the detectable limit (BDL) in four sub-districts, while Cr found in shrimps from Rupsa and Paikgacha were far higher than the maximum recommended limit defined by FAO and WHO. The average concentrations of Fe and Mn in all sub-districts crossed the recommendations, whereas average concentrations of Zn, Ni, Cd, and Pb were within the recommendations. Regardless of sampling site, target hazard quotients (THQ) of more than 1 contributed by Fe confirmed higher level of hazard index (HI), indicating potential human health risk. Fortunately, no heavy metal or their additive effect found to offer lifetime potency of carcinogenesis upon consumption of these shrimps. Therefore, probabilistic non-carcinogenic human health risk from Fe contamination necessitates stringent monitoring and controlling of this metal from different sources to farms.

Global warming is a threat across the world that leads to estimates of the upper thermal limits of ectothermic species. Increased water temperature up-regulates oxygen consumption and metabolic rates, and alters the physiological processes. In this study, we identified the critical thermal maxima (CTmax) and physiological responses under normoxia and hypoxia in Nile tilapia, Oreochromis niloticus. CTmax was 41.25 °C under hypoxia and 44.50 °C under normoxia. Compared to normoxia, lower values of hemoglobin (Hb) and red blood cells (RBCs) were observed at the CTmax under hypoxia. In contrast, higher values of white blood cells (WBCs) and blood glucose (Glu) levels were observed at the CTmax under hypoxia. Consequently, higher frequencies of micronucleus, cellular and nuclear abnormalities of erythrocytes were observed at the CTmax under hypoxia. These results suggest that high temperature tolerance and subsequent physiology are significantly affected by the oxygen supply in Nile tilapia. As climate vulnerability is intensifying day by day, this data will be helpful in successful management practice for the aquatic environment having low oxygen content.

Probiotics play an important role as bio-friendly substances in ensuring the sustainability and profitability of aquaculture. In the present study, we examined the effects of probiotic brewer's yeast, Saccharomyces cerevisiae on growth, feed utilization, hemato-biochemical indices, intestinal microbiota and intestinal morphometry of rohu, Labeo rohita. A trial of 90 days was conducted in which rohu fingerlings were fed under four different treatment groups in aquaria, receiving S. cerevisiae at 0, 1, 2 and 4 g/kg diet, respectively. Growth parameters (weight gain and specific growth rate), feed utilization (feed conversion ratio and protein efficiency ratio), hematobiochemical indices (hemoglobin, red blood cell, white blood cell and glucose), intestinal microbiota (total viable, lactic acid bacteria and yeast count) and intestinal morphology (villi length, villi width, crypt depth, thickness of villi wall etc.) were analyzed at the end of feeding trial. The results demonstrated substantial development in the growth performance, feed utilization and hematobiochemical indices in rohu fed probiotic incorporated diet compared to control diet. There were noticeable variations in intestinal microbiota and intestinal morphology between the treated and control diet fed groups. These results revealed that S. cerevisiae has a potential influence as an essential probiotic to improve the digestion, absorption, assimilation of nutrients through the improvement of gut microbiota and morphometry of L. rohita. Thus, S. cerevisiae can be effectively recommended as an important growth promoter for rohu.

Probiotics, an eco-friendly alternative to antibiotics application appears to have strong potential for improving the sustainability of aquaculture. The aim of the study was to evaluate the effect of probiotic brewer’s yeast, Saccharomyces cerevisiae supplementation on growth performance, feed utilization and intestinal morphometry of Nile tilapia, Oreochromis niloticus. A feeding trial of 60 days was conducted in which tilapia fingerlings (7.55 ± 1.25 g) were randomly distributed into three replicate aquaria under four different treatment groups, receiving S. cerevisiae at 0, 1, 2 and 4 g kg−1 diet, respectively. At the end of the feeding trial, growth performance parameters (weight gain, WG; % WG; specific growth rate, SGR), feed utilization indices (protein efficiency ratio, PER; feed conversion ratio, FCR) and intestinal morphology were assessed. The results obtained from this study revealed that growth performance and feed utilization indices were increased significantly in the fish fed with 4 g kg−1 S. cerevisiae supplemented diet compared to controls. The length, width and area of villus were significantly enlarged in fish fed 4 g kg−1 S. cerevisiae supplemented diet. Likewise, intestinal mucosal fold, width of lamina propria, width of enterocytes and number of goblet cells increased in the fish fed with 4 g kg−1 S. cerevisiae supplemented diet. These results demonstrated that S. cerevisiae can be effectively recommended as an important growth promoter for tilapia culture.