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For successful aquaculture, the primary need is the quality of fish feed, which determines fish flesh quality. The current study was conducted to evaluate the number and concentration of heavy metals in commonly used fish feeds and fish gills, liver, and muscle of biofloc technology and earthen pond systems. Besides this, the correlation between heavy metals in fish feeds with detected metals in the gills, liver, and muscle of fish was also determined. Results revealed that heavy metals concentration, including Cu and Cd, in feed B was significantly greater than in feed A, but the Zn level in feed A was significantly higher than in feed B. Furthermore, the concentration of heavy metals in fish of both aquaculture systems was significantly higher in the liver than in the gills and muscle. The metal concentration in fish feeds and fish edible parts (muscle) was lower than the WHO standard level; however, the amount of Pb was higher in the fish muscle, which is harmful for human consumption. Though the correlation test revealed that all of the metals from the feeds were positively correlated to the metals detected in the fish, but most of the estimated correlation was insignificant. From the current study, it can be concluded that the fish feed producers need to measure feed quality adequately to avoid hazardous contamination by heavy metals in the feed. The ultimate consumer, fish and humans, may, otherwise, be predisposed to assimilate and accumulate these heavy metals.

In aquaculture studies, Spirulina can be used to replace fish meal in aquafeed to lower the cost of producing fish feed while adding therapeutic and health benefits. Proteins, carbohydrates, vitamins, minerals, pigments, and fatty acids from Spirulina could enhance the cellular and humoral immunities of a variety of fish species. This review focuses on the functions of various Spirulina components that play a role in haematopoiesis, haemato-biochemical variables, pro-inflammatory and anti-inflammatory cytokine production, stress prevention, disease resistance, and immune responses in a variety of finfish species. Herein, we also presented the overlooked areas on the functionality of Spirulina on the immune response pathway and connected the missing link with the help of a better knowledge of the mammalian system, albeit these must be proved experimentally. This review will inspire the scientific community to investigate the biological role of Spirulina in fish, which is critical to the commercial viability of Spirulina as fish feed.

Fish feed quality is the main determinant of fish flesh quality, so it is important for successful aquaculture. The current study determines the concentration of heavy metals in fish feeds (A and B), water, and their bioaccumulation in gills, liver, and muscle of C. carpio cultured in different environments (biofloc technology and earthen pond systems). In addition, the correlation between heavy metals in fish feeds with bioaccumulated metals in fish tissues was also determined. Results revealed that most heavy metal concentration was significantly greater ( P  < 0.05) in feed B than in feed A but in permissible range, while all the heavy metal concentration was notably higher in earthen ponds than in biofloc technology. Result from the bioaccumulation factor and concentration of the metals showed that heavy metals were highly accumulated in the fish liver followed by gills. The metal concentration in fish feeds and fish edible parts (muscle) was lower than the WHO standard level; however, the amount of Pb was higher in the fish muscle, liver, and gills, which is harmful for human consumption and also for fish health. Though the correlation test revealed that all of the metals from the feeds were positively correlated to the metals in fish tissues, but most of the estimated correlation was significant and linearly correlated. It can be concluded that producers must measure feed quality correctly to avoid heavy metal contamination because it may assimilate and accumulate in the food chain.

Aflatoxins are fungal metabolites that contaminate foods and feeds, causing adverse health effects in humans and animals. This study determined the occurrence of aflatoxins in fish feeds and their potential effects on fish. Eighty-one fish feeds were sampled from 70 farms and 8 feed manufacturing plants in Nyeri, Kenya for aflatoxin analysis using competitive enzyme-linked immunosorbent assay. Fish were sampled from 12 farms for gross and microscopic pathological examination. Eighty-four percent of feeds sampled tested positive for aflatoxins, ranging from 1.8 to 39.7 µg/kg with a mean of 7.0 ± 8.3 µg/kg and the median of 3.6 µg/kg. Fifteen feeds (18.5%) had aflatoxins above the maximum allowable level in Kenya of 10 µg/kg. Homemade and tilapia feeds had significantly higher aflatoxin levels than commercial and trout feeds. Feeds containing maize bran and fish meal had significantly higher aflatoxin levels than those without these ingredients. Five trout farms (41.7%) had fish with swollen abdomens, and enlarged livers with white or yellow nodules, which microscopically had large dark basophilic hepatic cells with hyperchromatic nuclei in irregular cords. In conclusion, aflatoxin contamination of fish feeds is prevalent in Nyeri, and may be the cause of adverse health effects in fish in this region.

Heavy metal bioaccumulation in organisms is primarily a result of dietary uptake. The current study examines the concentrations of heavy metals (Pb, Cd, Cr, and Cu) in fish feed, water, sediment, and three fish species ( Catla catla , Labeo rohita , and Cyprinus carpio ) from different feeding zones in a polyculture pond system. Furthermore, associated human health risks were also evaluated. The fish samples ( n  = 25 for each species) were collected from 10 different fish ponds in the Kohat district, Pakistan. Heavy metals were determined using an atomic absorption spectrometer. Results revealed higher concentrations of heavy metals in sediment, followed by water. However, the concentration of heavy metals in fish feed was lower than the standard limits. In the case of fish, the bottom feeder ( C . carpio ) notably exhibited higher ( P  <  0 . 05 ) levels of heavy metals than the column feeder ( L . rohita ) and surface feeder ( C . catla ) fish. Moreover, in the liver of all fish species, the bioaccumulation of heavy metals was higher, followed by the gills. Principal component analysis (PCA) demonstrated a strong correlation of heavy metals in C . carpio gills, flesh, feed, and pond water, while the heavy metals in the liver correlated with the detected metals in sediment. The human health risk analysis shows that bottom feeder fish had higher estimated daily intake (EDI), target hazard quotient (THQ), and hazard index (HI) values (> 1). Consequently, the exposed population may experience adverse health effects. The findings of this study suggest that the bottom feeder ( C . carpio ) bioaccumulates a higher concentration of heavy metals than column ( L . rohita ) and surface feeder ( C . catla ) in the polyculture system.

Fish meat is a major and rich source of white protein; its quality is determined by the fish feed. However, the low-quality feed may contribute to a source of contamination if it does not fulfill the standard protocol. Biofloc is considered one of the most efficient, successful aquacultures, but this system is still under investigation for its efficiency and safety. Thus, current study focused on the heavy metal contamination in biofloc fish fed on different commercial feeds and human health risk analysis. Samples of extensively used three feeds (Supreme™, Hitech™, and MH-Aqua™), tanks water, and biofloc fish (gills, liver muscle) were collected for heavy metals (Cu, Cd, Pb, and Cr) analysis using atomic absorption spectrometry. An experiment was designed by dividing the fish into three groups: group 1 (Supreme™), group 2 (Hitech™), and group 3 (MH-Aqua™). A bioaccumulation factor and human health risk assessment have been calculated to measure fish and human health. Results revealed that most of the heavy metal concentration was higher (P < 0.05) in MH-Aqua™ feed compared to others. Similarly, heavy metal concentration was higher (P < 0.05) in the water of group 3, where fish was cultured on MH-Aqua™ feed. However, in the fish gills, liver, and muscle, the heavy metal concentration was significantly greater in group 3 fed on MH-Aqua™ feed, followed by group 1. Heavy metals in all feeds were positively correlated to the heavy metal concentration of the fish muscles. The bioaccumulation factor for Cu and Pb was higher in the fish liver, Cd and Cr in the case of fish gills, and least in the fish muscle. EDI and THQ values vary in all the groups, while the HI value was found lower than 1 in group 1 and group 2 but higher in group 3 fed on MH-Aqua™ feed. Strict checks and balances in formulating a diet will be helpful to progressively lower the amount of dangerous heavy metals.

The use of plant-based fish feed may increase the risk of contamination by mycotoxins. The multiresidue analysis of mycotoxins in fish feed presents many difficulties due to the complexity of the matrix, the different characteristics of the compounds, and their presence in highly different concentration levels. The aim of this study was to develop a selective, sensitive, and efficient analytical method for the simultaneous determination of 15 mycotoxins (regulated and emerging mycotoxins) in aquaculture feed by LC-MS/MS. Sample extraction was performed with ultrasonic assistance, and different cleanup strategies were evaluated. The optimized method was composed by ultrasound-assisted extraction (two cycles, 55 °C, 20 min), followed by cleanup using a Captiva EMR Lipid cartridge. Then, nine commercial samples of aquaculture fish feed were analyzed. Eight of the 15 target mycotoxins were detected in the samples. Results showed that two enniatins (EENB and ENNB1), beauvericin, and fumonisin B2 were detected in all samples. These results show the multi-mycotoxin contamination of fish feed, highlighting the need to improve current knowledge on the occurrence and toxicity of mycotoxins in fish feed, mainly the emerging ones.

The first part of this study evaluates the occurrence of mycotoxin patterns in feedstuffs and fish feeds. Results were extrapolated from a large data pool derived from wheat (n = 857), corn (n = 725), soybean meal (n = 139) and fish feed (n = 44) samples in European countries and based on sample analyses by liquid chromatography/tandem mass spectrometry (LC-MS/MS) in the period between 2012–2019. Deoxynivalenol (DON) was readily present in corn (in 47% of the samples) > wheat (41%) > soybean meal (11%), and in aquafeeds (48%). Co-occurrence of mycotoxins was frequently observed in feedstuffs and aquafeed samples. For example, in corn, multi-mycotoxin occurrence was investigated by Spearman’s correlations and odd ratios, and both showed co-occurrence of DON with its acetylated forms (3-AcDON, 15-AcDON) as well as with zearalenone (ZEN). The second part of this study summarizes the existing knowledge on the effects of DON on farmed fish species and evaluates the risk of DON exposure in fish, based on data from in vivo studies. A meta-analytical approach aimed to estimate to which extent DON affects feed intake and growth performance in fish. Corn was identified as the ingredient with the highest risk of contamination with DON and its acetylated forms, which often cannot be detected by commonly used rapid detection methods in feed mills. Periodical state-of-the-art mycotoxin analyses are essential to detect the full spectrum of mycotoxins in fish feeds aimed to prevent detrimental effects on farmed fish and subsequent economic losses for fish farmers. Because levels below the stated regulatory limits can reduce feed intake and growth performance, our results show that the risk of DON contamination is underestimated in the aquaculture industry.

Hop acids are known for their potent antimicrobial properties and may offer significant benefits in aquaculture. As hop acids are a prominent component of spent brewer's yeast, a major byproduct of the brewing industry, their utilization in fish feed holds potential for enhancing both the economic and environmental sustainability of aquaculture operations, provided they are not detrimental to the growth and quality of the product. A 56‐day nutritional trial was conducted that incorporated hop acids (Humulone and Lupulone) into the diets of Nile tilapia, Oreochromis niloticus, and assessed their effects on rearing production, lysozyme activity, and final fillet LAB color & aroma. Four experimental diets containing between 0 and 1200 mg hop acids/kg feed were formulated for the nutritional study. Ninety‐six tilapias were distributed equally among twelve ~2000 L tanks (eight fish/tank) and randomly assigned a treatment diet with 3 tanks per treatment (n = 3). Fish were weighed weekly and fed daily. After the trial, various production metrics, including weight gain, feed conversion ratio, viscerosomatic index, hepatosomatic index, condition factor, and fillet yield, were assessed. Additionally, lysozyme activity was assessed in isolated serum samples. Skinned and deboned fillets were assessed for LAB color, and a sensory panel evaluated the aroma of raw and baked fillets. The study revealed the inclusion of hop acids provided no significant differences in the production metrics, except for the viscerosomatic index. While not reflected in the FCR, weekly weight measurement found that the feed treatment of approximately 300 hop acids/kg of feed had slightly higher average fish weight per tank toward the end of the feed trial. There were minor differences in color, but no significant differences in aroma between treatment and control fillets. Incorporating hop acids into the diet, even at the highest inclusion level tested, did not result in any adverse effects on the fish. While these findings do not show significant benefits of hop acid addition, there were no detrimental effects, suggesting a promising avenue for utilizing brewing waste streams or isolated hop acids as an effective supplement in fish feed formulations.

This study aimed to identify the bioactive compounds present in Kappaphycus alvarezii ethanol extracts using various solvent ratios, through GC-MS analysis and antioxidant activity assays. The ultimate goal is to provide critical insights supporting the application of K. alvarezii extract as a feed additive in the diet of Nile tilapia (Oreochromis niloticus). The research was conducted in two experimental phases. Phase 1 involved the preparation of ethanol extracts using three different solvent ratios: 1:3 (A), 1:4 (B), and 1:5 (C). Each extract was analyzed using Gas Chromatography-Mass Spectrometry (GC-MS) to profile the chemical constituents, followed by evaluation of their antioxidant activity. Phase 2 assessed the application of these ethanol extracts in commercial fish feed over a 40-day rearing period. Four dietary treatments were tested: commercial feed only (P1), and commercial feed supplemented with K. alvarezii extract at ratios of 1:3 (P2), 1:4 (P3), and 1:5 (P4). A Completely Randomized Design (CRD) with three replicates per treatment was employed, resulting in a total of 12 experimental units. Growth performance and survival rate of Nile tilapia were evaluated. GC-MS profiling revealed that the ethanol extracts were dominated by palmitic acid (hexadecanoic acid), a compound known for its antioxidant potential. The extract with a 1:3 solvent ratio exhibited the strongest antioxidant activity, with an IC50 value of 34.66 ppm. Application of this extract in fish feed significantly influenced growth and survival performance. The 1:3 treatment yielded the best results, enhancing absolute weight gain (4.51±0.47 g), specific growth rate (1±0.07%/day), and achieving a 100% survival rate. Additionally, this treatment improved the fish's health status, as indicated by elevated erythrocyte counts (306,000 cells µL-) and hematocrit levels (25.7%).