https://janb.guilan.ac.ir/ Aquatic Animals Nutrition en daily 1 Tue, 04 Nov 2025 00:00:00 +0330 Tue, 04 Nov 2025 00:00:00 +0330 https://janb.guilan.ac.ir/article_9116.html Introduction: Sustainable aquaculture relies on balanced diets that ensure optimal growth and health. Nanotechnology applications in aquaculture, such as using selenium and iron nanoparticles (Se-NPs, Fe-NPs), show promise for enhancing nutrition. However, their combined effects on intestinal health in beluga are unclear. Therefore, this study aimed to investigate the individual and combined effects of different dietary levels of Se-NPs and Fe-NPs on the intestinal histopathology of juvenile beluga, to identify the optimal and safest supplementation ratio. Materials and methods: A total of 135 beluga juveniles (with an initial weight of 276.4 ± 32.3 g and an initial length of 40 ± 2 cm) were randomly distributed in 27 fiberglass tanks at 9 different treatments with 3 replicates. Treatments included T1 (control, no added NPs), T2 (1 mg/kg Se-NPs), T3 (2 mg/kg Se-NPs), T4 (100 mg/kg Fe-NPs), T5 (100 mg/kg Fe-NPs +1 mg/kg Se-NPs), T6 (100 mg/kg Fe-NPs +2 mg/kg Se-NPs), T7 (200 mg/kg Fe-NPs), T8 (200 mg/kg Fe-NPs +1 mg/kg Se-NPs), and T9 (200 mg/kg Fe-NPs +2 mg/kg Se-NPs). Before starting the experiment, the fish were adapted to the rearing conditions for a week. The amount of feed during the rearing period was 2-3% of the fish's weight, adjusted according to water temperature. The fish were fed three times a day (8:00-15:00 and 21:00) for 8 weeks. To find the histopathological changes, six fish intestine tissues from each group (two fish of each replicate) were sampled at the end of the experiment. Samples were dehydrated by routine methods and embedded in paraffin wax. They were sectioned by microtome and stained with Hematoxylin and Eosin (H&E). Results and discussion: Histopathological examination revealed intestinal alterations including villi degeneration, inflammatory cell infiltration in both submucosal and muscular layers, hyperemia, and necrosis. Evaluation of treatment responses showed that the combination of 100 mg/kg Fe-NPs with 1 mg/kg Se-NPs (T₅) demonstrated the most favorable outcome, with tissue integrity comparable to the control group. The T₈ treatment also showed relatively preserved intestinal morphology. In contrast, treatments with higher nanoparticle concentrations exhibited significantly more severe pathological changes, including prominent hyperemia and inflammatory infiltration. These findings indicate that the 100:1 Fe-NPs to Se-NPs ratio effectively mitigates the adverse effects of both elements. Conclusions: It is concluded that the combined use of iron and selenium nanoparticles at doses of 100 mg/kg Fe-NPs and 1 mg/kg Se-NPs in the diet of beluga is the most appropriate and optimal combination, resulting in minimal histopathological damage to the intestinal tissue. This ratio effectively balances the pro-oxidant potential of iron with the antioxidant capacity of selenium, thereby preserving intestinal health and integrity. Conflicts of interest: The authors have no conflicts of interest to declare for the publication of the present work. Funding: This article is a part of the project number 12-32-12-011-98001-991148, which was carried out with the agricultural research education and extension organization (AREEO). Acknowledgments: The authors are grateful to researchers of the International Sturgeon Research Institute for their support during this study. https://janb.guilan.ac.ir/article_9118.html Introduction: Fish feeding is typically composed of various ingredients, some of which may be contaminated with chemical hazards, especially heavy metals, due to environmental pollution or poor processing practices. For instance, researchers demonstrated that the distribution of heavy metals in fish tissues is significantly influenced by the metal load present in water, sediment, and feedstuffs that contaminated final product. Many commercial feed producers fail to meet safety standards, leading to the incorporation of contaminated raw materials into fish feed. The feed used in aquaculture is crucial and has a significant impact on the health and quality of aquatic organisms, which in turn affects public health for humans. If the feed for aquatic animals is exposed to chemical contaminants, it poses risks not only to the health of the fish but also to the final consumers. Chemical hazards in aquaculture can lead to bioaccumulation in fish, ultimately affecting the end consumers of these products. Description: Contaminants such as heavy metals, mycotoxins, persistent organic pollutants, and veterinary drug residues are prevalent in aqua feeds and can accumulate in fish tissues, leading to food safety concerns. For instance, researchers highlight the presence of metals such as mercury and cadmium in fish feeds, which can adversely affect the quality of aquaculture products. Mycotoxin contamination in plant-based feed ingredients can lead to significant health issues in fish and, consequently, in humans consuming these fish. The World Health Organization has reported that a significant percentage of diseases in human populations worldwide can be attributed to prolonged exposure to environmental pollutants, including heavy metals. This highlights the urgent need to monitor and regulate heavy metal levels in aquatic environments to safeguard both fish health and public health. In communities where fish consumption is higher due to its nutritional value, the risk of exposure to heavy metals is also increased. Therefore, assessing the health risks associated with heavy metal exposure in fish consumption guidelines is essential for informing consumers about potential dangers. The bioaccumulation of heavy metals is influenced by several factors, including the fish species, the concentration of metals in the environment, and the duration of exposure. For instance, benthic fish species typically exhibit higher levels of heavy metals compared to pelagic species due to their feeding habits and exposure to sediments that are often rich in pollutants. This accumulation of heavy metals can result in biological residues, where larger fish, higher in the food chain, accumulate greater concentrations of these toxic substances, thereby increasing the health risks associated with the consumption of such fish. By understanding the pathways of contamination and implementing effective remediation and management practices, the aquaculture industry can work towards ensuring the safety and sustainability of fish farming practices. The transition from traditional fishmeal-based feeds to alternative protein sources, coupled with effective waste management and the use of probiotics, can significantly reduce the ecological footprint of aquaculture. By prioritizing sustainability in feed formulation and aquaculture practices, the industry can contribute to the conservation of marine resources, enhance food security, and promote the health of aquatic ecosystems. Conclusion: In conclusion, the presence of contaminants in aquaculture feed sources is a multifaceted issue that poses significant risks to aquatic ecosystems and human health. Heavy metals, mycotoxins, and persistent organic pollutants are prevalent in aqua feeds and can lead to bioaccumulation in fish, ultimately affecting consumers. Addressing these challenges requires a concerted effort from producers, regulators, and researchers to ensure the safety and sustainability of aquaculture practices. Today, in light of the importance of reducing chemical pollutants and hazards in food for both humans and animals, it is crucial to implement control and monitoring measures for raw materials and complete feed for aquatic organisms within the commercial feed production chain in manufacturing facilities. To address this issue, permissible limits, also referred to as maximum tolerable levels, are established for these substances. https://janb.guilan.ac.ir/article_9119.html Introduction: Rainbow trout, Oncorhynchus mykiss belongs to the Salmonid family, one of the important domestic species in freshwater. High-energy diets with approximate levels of 45-50% protein and 18-24% fat are considered to meet their demands. However, due to the limited availability of fish oil, it cannot be considered a sustainable fat source in aquaculture. Meanwhile, fat powder can be used as an available and sustainable alternative in the diet, but due to the presence of saturated fatty acids, it has low digestibility, which may adversely affect fish health and growth. Thus, suitable additives might increase the possibility of replacing fat powder in the diet. Additionally, the amino acid taurine plays a crucial role in the formation of bile salts, which are essential for the digestion and absorption of intestinal fats. This study aims to investigate the effect of supplementary taurine on the growth, body composition, and fat digestibility of rainbow trout fed fat powder, with a focus on optimizing aquaculture productivity and sustainability. Materials and Methods: Experimental diets included a positive control containing fish oil, canola oil and other diets containing fat powder (about 70% of the fat source was provided) supplemented with taurine at doses of 0 (negative control), 5, 10, and 20 g/kg (T0, T5, T10 and T20, respectively). A total of 225 rainbow trout with an average initial weight of 12 ± 0.03 g were distributed in 15 rearing tanks based on a completely randomized design for 58 days. Fish were fed three times a day at 8:00, 12:00 and 18:00 until apparent satiation. After 24 hours of stop feeding, the approximate amount of body composition (sampling of three fish from each tank at the end of the experiment) and items including protein, moisture, total fat and ash were measured followed by the procedure of AOAC (2005). At the end of the experiment, in order to evaluate the apparent digestibility of nutrients, fish were fed with diets containing chromic oxide. Then, feed and feces were collected and analyzed according to the method described by Austreng (1978). SPSS software (version 19.0) was used for statistical analysis. Data were presented as the mean of 3 replicates ± standard deviation using the Duncan post-hoc test to compare means of each treatment. Results: The results of growth parameters showed that T20 exhibited in a significant increase in final weight, percentage of weight gain and specific growth rate compared to the negative control (T0; P<0.05) Feed conversion ratio, feed intake, protein efficiency, condition factor and survival rate were not affected by the experimental diets (P<0.05). According to the result of body composition, fat, protein and ash contents were affected by the different levels of taurine (P<0.05), but moisture did not show a significant difference between the experimental treatments (P<0.05). T20 resulted in an increase in protein and fat compared to the negative control (P<0.05). Body fat content was higher in the positive control than in the other groups (P<0.05). The lowest body fat content was related to T20. (P<0.05). Body protein was improved in T20 similar to the positive control (P<0.05), and the lowest amount of protein was found in the negative control (P<0.05). The ash content in the positive control was significantly higher than in the negative control (P<0.05). Furthermore, T20 led to an increase in protein digestion, while the lowest value was observed in the negative control (P<0.05). The fat digestibility was negatively affected by fat powder inclusion. However, it could be improved to some extent when taurine was supplemented. The highest ash content was found in T20 whereas the lowest in the negative control (P<0.05). Discussion: The results of the present study indicate that the addition of 20 g/kg taurine to a diet containing fat powder (T20) improves the growth performance of fish. This improvement is likely due to the enhanced fat digestion and better fat utilization as an energy source. Furthermore, T20 resulted in elevated body protein and fat content. Although the body fat in fish treated with the positive control was higher than in the other treatments, T20 seems to fully compensate the body protein levels. The increased body fat suggests improved digestibility of fat powder under the influence of taurine. Taurine has a significant role in enhancing fat digestion by binding to bile acids, leading to the formation of bile salts. These bile salts are stored in the gallbladder and released into the intestine as required, facilitating the digestion and absorption of fats. Taurine increases protein synthesis by accelerating glycolysis and fulfills the growth requirements of the fish body through intense oxidative glucose breakdown or its conversion into amino acids. The current findings showed that protein digestibility improved by diets containing 10 and 20 g/kg taurine (T10 and T20). On the other hand, the inclusion of fish oil in the diet, due to its polyunsaturated fatty acids with multiple double bonds, demonstrates greater digestibility compared to fat powders. The observed reduction in digestibility in the negative control group can be attributed to the insufficiency of bile salts, but this could be compensated by the addition of taurine. Conclusion: Given the results, it can be concluded that the addition of taurine successfully improved the digestibility of fat powder in the diet of rainbow trout. As a result, taurine enhanced fat absorption, and at the level of 20 g/kg taurine, it also improved protein digestibility. These improvements led to enhanced growth performance and increased body protein in rainbow trout. https://janb.guilan.ac.ir/article_9147.html Introduction: Bioactive compounds in plants are essential for aquatic animal nutrition because of their antioxidant and anti-inflammatory effects. They combat oxidative stress by neutralizing free radicals, protecting cells from damage. This protection helps maintain normal physiological functions critical for fish health. Furthermore, these compounds enhance the immune system, increasing fish resistance to pathogens and environmental stressors. Improved immunity reduces disease risk and mortality rates. Bioactive substances also support digestion and nutrient absorption, promoting better growth performance. Collectively, they boost fish resilience and biological functioning, making them valuable for sustainable aquaculture.Materials and Methods: To examine the effects of ivy leaf extract, three dietary treatments with 100, 150, and 200 mg/kg extract (T100, T150 and T200, respectively) were prepared along with a control basal diet without extract (T0). Ingredients for the basal diet were precisely weighed and mixed, with the extract added accordingly. Pellets were made by mixing the ingredients, forming dough with water, grinding through a 2.4 mm pellet, air-drying, and storing at 4 °C. Two hundred and forty rainbow trout averaging 6.39 ± 0.35 g were acclimated for two weeks in 12 glass aquariums stocked with 20 fish each. After acclimation, tanks were randomly assigned to treatments with three replicates for an 8-week trial. Fish weights were measured biweekly to adjust feeding. Water quality was maintained with aeration, daily 70% water exchange, and stable temperature (13 ± 1°C), oxygen (8 ± 0.43 mg/L), and pH (7.5 ± 0.5). At the end, fish were anesthetized for biometric measurements, and growth indices including weight gain, specific growth rate, daily weight gain, and feed conversion ratio were calculated. Mucus was collected from six fish per treatment by gentle rubbing in saline solution, centrifuged, and stored at -70 °C. Immune assays measured lysozyme activity through bacterial lysis, total immunoglobulin by precipitation and protein quantification, and complement activity by rabbit red blood cell lysis. Data were statistically analyzed using tests for normality, variance, One-Way ANOVA, and Duncan’s multiple comparison with significance at P < 0.05.Results and Discussion: The study found that adding ivy leaf extract significantly improved growth performance in rainbow trout, with the highest final weight and weight gain in T200. Immune responses in the mucus showed increased complement activity at T150 and higher total immunoglobulin and protein levels proportional to extract dose, peaking at T200. Lysozyme activity was significantly elevated only in the highest dose group. Feed conversion ratio improved significantly at T200, while lower doses had mixed effects. These findings demonstrate the dose-dependent benefits of ivy leaf extract on growth and mucosal immunity in rainbow trout. Herbal feed additives are an eco-friendly way to boost immunity and health in aquatic animals. Plants contain bioactive compounds like organic acids, flavonoids, and polyphenols that improve fish immune responses and overall wellbeing. In this study, ivy leaf extract enhanced growth and mucosal immunity in rainbow trout, likely by reducing oxidative stress and promoting energy use for growth. Ivy leaf extract increased lysozyme activity—a natural antibacterial enzyme—and raised total protein and immunoglobulin levels in skin mucus, strengthening the first line of defense. Polyphenols in plants support mucus production and quality, important for protecting against pathogens.Conclusion: Plant extracts offer a sustainable alternative to antibiotics in aquaculture by improving innate and mucosal immunity. The study recommends 200 mg/kg ivy leaf extract supplementation for enhancing immune health in rainbow trout fingerlings. https://janb.guilan.ac.ir/article_9135.html Introduction: Selenium (Se) has recently received considerable attention in aquatic nutrition. Farmed fish are exposed to various stressors, making nutritional supplements crucial management tools for enhancing stress resistance and optimizing overall health parameters. To reduce the overuse of antibiotics, researches have focused on dietary additives such as selenium to enhance fish health. The incorporation of prebiotics into aquatic diets is an emerging strategy for diseases prevention and enhanced production. Selenium-rich prebiotic yeast combines the benefits of both prebiotic and organic selenium, potentially exerting dual effects. The present study is the first to compare the effects of three selenium yeast types, Selemax, Selensource and Sel-Plex, on growth performance, carcass composition and stress resistance in common carp. Materials and Methods: In this study, the effects of seven diets containing 0.3 mg Se from Selemax, 1 mg Se from Selemax, 0.3 mg Se from Selenosource, 1 mg Se from Selenosource, 0.3 mg Se from Sel-Plex, 1 mg Se from Sel-Plex per kg of diet, and a control diet without Se supplementation were investigated in common carp (Cyprinus carpio). Each dietary treatment was studied in 2 tanks (replicates) and each tank contained 31 fish with an initial weight of 1.61 ± 0.32 g (mean ± SD) in a completely randomized design. Results: No significant differences were observed in fish weight, standard length, and condition factor (P>0.05). Selenium yeast supplementation did not significantly affect survival rate during the rearing period and carcass dry matter, crude protein and crude fat (P>0.05). However, feeding with 0.3 mg of Se in the form of Selenosource significantly reduced the carcass ash percentage (P<0.01). After exposure to high-intensity salinity stress (without aeration), no significant differences in survival time were observed (P>0.05).  In contrast, under low-intensity salinity stress (with aeration) survival time increased significantly in fish fed with 0.3 mg Se in the form of Selemax or Sel-Plex (P<0.05). Discussion: The insignificant difference in the survival rate of the fish indicated suitable rearing conditions. The effect of selenium yeast on the fish growth in different studies is somewhat contradictory and depends on the composition of the feed, experimental conditions, form and concentration of selenium and the health, species and life stage of the fish. While higher levels of selenium yeast will lead to significant differences in the growth of common carp but based on the new standard, selenium consumption is limited and high selenium concentration in the feed causes its accumulation in the environment and environmental problems. Selenium influences lipid, carbohydrate and amino acid metabolism in aquatic animals, but many studies have shown that selenium supplementation has no effect on the proximate analysis of fish. However, in some studies the effect of selenium on the amounts of protein and ash in the carcass has been proven. It seems that the difference in the formula of the diets is an important factor in observing different results even in the same species, since selenium is absorbed more effectively in the presence of other compounds such as vitamins E, D and A. In addition, proteins and fats also affect the bioavailability of selenium. Numerous studies in fish have shown that dietary selenium supplementation can mitigate oxidative stress caused by stressful conditions, however, the type of stressor influences outcomes even within the same species. Despite the beneficial effects of dietary selenium on fish, it has been reported that high dietary intake can lead to a decrease in antioxidant capacity, and this may be why in the present study, fish receiving 0.3 mg Se in the form of Selemax or Sel-Plex performed better than fish fed 1 mg of these types of selenium. Overall, the mechanism by which high selenium intake impairs the antioxidant system in aquatic animals remains unclear. Conclusion: This study highlights the importance of dietary selenium supplementation for fish health and welfare. Although fish fed the unsupplemented control diet exhibited good growth and a high survival rate compared to the other fish, the basal selenium level was insufficient confer protection against stress. Dietary selenium supplementation enhanced stress resistance. Overall, the use of Selenosource selenium yeast in the diet of common carp was not beneficial but the application of selenium yeast with the brands Selemax or Sel-Plex at a level of 0.3 mg per kg of diet is recommended to increase resistance against stress. https://janb.guilan.ac.ir/article_9162.html Introduction: Grass carp, Ctenopharyngodon idella, is considered one of the most commercially important farmed fish in the world. One of the important factors in the development of aquaculture is to provide a suitable ration that can meet the nutritional requirements of this fish, and on the other hand, the ration should be as cheap as possible so ultimately to achieve cheaper food by optimizing the food ration. In this research, the effect of different levels of soybean meal and canola on growth parameters and carcass composition of grass carp fingerlings with an average initial weight of 7.56 ± 1.12 g (mean ± SD) were investigated for 60 days. Materials and methods: Experiments were conducted in 100-L fiberglass tanks containing 7 grass carp fingerlings in 3 repetitions, with a total of 9 experimental tanks. The three treatments included Treatment 1 (T1) with a diet containing 24.5% soybean meal and 24.5% canola meal, Treatment 2 (T2) with 29% canola meal and 21% soybean meal, and Treatment 3 (T3) with 28% soybean meal and 20% canola meal. The tanks were divided completely randomly. Results and discussion: According to Duncan test, differences were observed between the treatments in terms of mean food conversion ratio (FCR), specific growth rate, and weight gain (P<0.05). The results showed that the maximum and minimum amounts of weight gain were occurred in T3 (89.91 ± 2.4 g) and T2 (58.39 ± 13.17 g), respectively. The minimum of special growth rate (0.70 ± 0.15 %/day) was observed in T2, while the maximum (1.06 ± 0.02 %/day) in T3. The minimum average of FCR (2.09 ± 0.05) was found in T3 while the maximum (3.69 ± 1.09) in T2. The results obtained from the Kruskal-Wallis test did not exhibit any significant difference among different treatments in terms of the biochemical composition of the fingerling carcasses, including protein, fat, ash, and moisture contents (P<0.05). Conclusion: According to the obtained results, it seems that 28% soybean meal and 20% canola are the most suitable levels in the diet of grass carp fingerlings.