Zinc uptake in fish intestinal epithelial model RTgutGC: Impact of media ion composition and methionine chelation

Fe-NPs and Zn-NPs: Advancing Aquaculture Performance Through Nanotechnology

Aquaculture is a growing industry facing several challenges, including disease control, water quality management, and sustainable feed production. One potential solution to these challenges is the use of trace elements such as iron (Fe) and zinc (Zn), either in their conventional form or as nanoparticles (NPs). Aquatic animals need these micronutrients for normal growth, physiological processes, and overall health. In marine species, iron boosts development, immunity, and disease resistance. At the same time, zinc enhances metabolism, synthesizes essential enzymes, and produces hormones that play a part in defenses, growth, reproduction, and antioxidative activities. According to this review, species-specific requirements by different Fe and Zn compounds have all emphasized the impacts on animal growth and development, antioxidant capacity, reproductive efficiency, and immunological response. However, NPs of Fe and Zn have been found to have higher bioavailability and efficacy than conventional forms. This work examines the effects of applications of Fe and Fe nanoparticles (Fe-NPs) and Zn and Zn nanoparticles (Zn-NPs) in aquaculture. However, the source of Fe and Zn in aquaculture species and administration volume may significantly impact efficacy. Nanotechnology boosts the positive benefits of Fe and Zn by converting them to their nanoforms (Fe-NPs) and (Zn-NPs), which are better used by animals and have a broader intake range. As a result, Fe-NPs and Zn-NPs offer an effective method for using nutrients in aquaculture.

Responses to graded levels of zinc amino acid complex in Nile tilapia (Oreochromis niloticus)

Zinc (Zn) is an essential micronutrient that plays a crucial role in fish development and physiology. This study aimed to evaluate the effects on growth and health in Nile tilapia (Oreochromis niloticus) supplemented with graded levels of zinc amino acid complex (Zn-AA) and subjected to transport stress. Nile tilapia (21.78 ± 0.17 g; (n = 12 fish per tank; stocking density of 1.045 kg- 3) were fed with 0, 25, 50, 75, or 100 mg Zn-AA kg- 1 (equivalent to 77.49, 102.69, 127.89, 153.09, or 178.29 mg Zn kg- 1) in extruded diets (280 g kg- 1 digestible protein; isoproteic and isocaloric) for 60 days. At the end of the experimental period, after growth performance measurements, the fish were transported by car for 3 h, and blood collection was performed. The linear regression showed that the best growth performance (final weight, final biomass, weight gain, specific growth rate, and feed intake) was found in fish fed with 100 mg Zn-AA kg diet- 1 (p < 0.05). The increased dietary Zn-AA increased linearly plasma triglyceride levels, hemoglobin, mean corpuscular hemoglobin, and leukocyte values and reduced plasma total protein, cholesterol (total and LDL), and aspartate aminotransferase levels (p < 0.05). According to quadratic regression, the highest plasma glucose and alanine aminotransferase values were found in the control group (p < 0.05). In conclusion, under the conditions of this study, 100 mg Zn-AA kg diet- 1 is recommended for Nile tilapia as it can improve their growth, metabolism, physiology, and immunity.

Physiological trade-off of marine fish under Zn deficient and excess conditions

Fish can regulate their Zn body bioaccumulation, but the mechanisms and physiological responses at the organ level are still largely unknown. In the present study, we exposed the marine seabreams under different Zn levels (deficient, optimum and excess levels) over a period of 4 weeks and examined how fish maintained its regulation of bioaccumulation with associated physiological effects at the fish intestinal organ. Our results indicated that fish intestinal organs constantly controlled the Zip family to "rob" more Zn under Zn-deficiency (with a dietary level of 7.9 mg/kg), whereas restricted the Zn efflux to preserve the intestinal function. Under Zn-excess conditions (193.3 mg/kg), the fish intestine maintained a limited Zn homeostasis (37.8-44.6 μg/mg) by initially inhibiting the influx through the Zip family receptor, but later accelerating both influx and efflux of Zn. Based on the WGCNA method, Zn deficient dietary exposure first resulted in defense response with subsequent switching to antioxidant defense. Instead, excess Zn first triggered the immunological response, but then led to physiological toxicity (abnormal in lipid metabolism). Although Zn had multiple biological functions, it was preferentially involved in lipid metabolism under different dietary Zn doses. This study provided direct evidence for Zn regulation at the organ level and detoxification mechanisms against potential environmental toxicity in fish.

Establishment of an In Vitro Model to Study Viral Infections of the Fish Intestinal Epithelium

Viral infections are still a major concern for the aquaculture industry. For salmonid fish, even though breeding strategies and vaccine development have reduced disease outbreaks, viral diseases remain among the main challenges having a negative impact on the welfare of fish and causing massive economic losses for the industry. The main entry port for viruses into the fish is through mucosal surfaces including that of the gastrointestinal tract. The contradictory functions of this surface, both creating a barrier towards the external environment and at the same time being responsible for the uptake of nutrients and ion/water regulation make it particularly vulnerable. The connection between dietary components and viral infections in fish has been poorly investigated and until now, a fish intestinal in vitro model to investigate virus-host interactions has been lacking. Here, we established the permissiveness of the rainbow trout intestinal cell line RTgutGC towards the important salmonid viruses-infectious pancreatic necrosis virus (IPNV), salmonid alphavirus (subtype 3, SAV3) and infectious salmon anemia virus (ISAV)-and explored the infection mechanisms of the three different viruses in these cells at different virus to cell ratios. Cytopathic effect (CPE), virus replication in the RTgutGC cells, antiviral cell responses and viral effects on the barrier permeability of polarized cells were investigated. We found that all virus species infected and replicated in RTgutGC cells, although with different replication kinetics and ability to induce CPE and host responses. The onset and progression of CPE was more rapid at high multiplicity of infection (MOI) for IPNV and SAV3 while the opposite was true of ISAV. A positive correlation between the MOI used and the induction of antiviral responses was observed for IPNV while a negative correlation was detected for SAV3. Viral infections compromised barrier integrity at early time points prior to observations of CPE microscopically. Further, the replication of IPNV and ISAV had a more pronounced effect on barrier function than SAV3. The in vitro infection model established herein can thus provide a novel tool to generate knowledge about the infection pathways and mechanisms used to surpass the intestinal epithelium in salmonid fish, and to study how a virus can potentially compromise gut epithelial barrier functions.

Role of the luminal composition on intestinal metal toxicity, bioavailability and bioreactivity: An in vitro approach based on the cell line RTgutGC

The bioavailability of metal complexes is poorly understood. To evaluate bioavailability and toxicity of neutral and charged complexes as well as free metal ions, Visual Minteq, a chemical equilibrium model, was used to design media containing different metal species. Two non-essential (silver and cadmium) and two essential (copper and zinc) metals were selected. The rainbow trout (Oncorhynchus mykiss) gut cell line (RTgutGC) was used to investigate bioavailability, bioreactivity and toxicity of the different metal species. Toxicity was measured using a multiple endpoint cytotoxicity assay, bioavailability by measuring intracellular metal concentration, and bioreactivity by quantification of mRNA level of the metal responsive genes, metallothionein (MT), glutathione reductase (GR) and zinc transporter 1 (ZnT1). Speciation calculations showed that silver and cadmium preferentially bind chloride, copper phosphate and bicarbonate, and zinc remained primarily as a free ion. Cysteine avidly complexed with all metals reducing toxicity, bioavailability and bioreactivity. Silver and copper toxicity was not affected by inorganic metal speciation, whereas cadmium and zinc toxicity was decreased by chloride complexation. Moreover, reduction of calcium concentration in the medium increased toxicity and bioavailability of cadmium and zinc. Bioavailability of silver and zinc was reduced by low chloride while cadmium bioavailability was increased by low chloride and in presence of bicarbonate. Copper bioavailability was not affected by the medium composition. Cadmium and silver were more bioreactive, independently from the medium composition, in comparison to copper and zinc (i.e., higher induction of MT and GR). Cadmium was the only metal able to induce MT in presence of cysteine. ZnT1 was induced by cadmium in low-chloride, by zinc in low-chloride low-calcium and by cadmium and copper in the bicarbonate media. Overall, this study demonstrates that metal complexation alone is not sufficient to explain metal toxicity, and that anion exchange mechanisms play a role in metal uptake and bioreactivity.

Effects of Zinc Status on Expression of Zinc Transporters, Redox-Related Enzymes and Insulin-like Growth Factor in Asian Sea Bass Cells

Since Asian sea bass is one of the economically most important fish, aquaculture conditions are constantly optimized. Evidence from feeding studies combined with the current understanding of the importance of zinc for growth and immune defense suggest that zinc supplementation may be a possible approach to optimize aquacultures of Asian sea bass. To investigate the effects of zinc deficiency and zinc supplementation, cells from Asian sea bass were incubated in culture medium with different zinc contents. The expression of genes, important for zinc homeostasis, redox metabolism, and growth hormones was analyzed using RT-PCR. Zinc deficiency induced the expression of certain zinc transporters (ZIP14, ZIP10, ZIP6, ZIP4, ZnT4, ZnT9) as well as of SOD1, IGF I and IGF II, while expression of ZnT1 and metallothionein (MT) was reduced. Zinc supplementation decreased the expression of ZIP10, while expression of ZnT1 and MT were elevated. No differences in the effects of zinc supplementation with zinc sulfate compared to supplementation with zinc amino acid complexes were observed. Thus, extracellular zinc conditions may govern the cellular zinc homeostasis, the redox metabolism and growth hormone expression in cells from Asian sea bass as reported for other fish species. Our data indicate that supplementing aquacultures with zinc may be recommended to avoid detriments of zinc deficiency.

Organic copper promoted copper accumulation and transport, enhanced low temperature tolerance and physiological health of white shrimp (Litopenaeus vannamei Boone, 1931)

This study was conducted to assess the effects of dietary copper source and level on hematological parameters, copper accumulation and transport, resistance to low temperature, antioxidant capacity and immune response of white shrimp (Litopenaeus vannamei Boone, 1931). Seven experimental diets with different copper sources and levels were formulated: C, no copper supplementation; S, 30 mg/kg copper in the form of CuSO₄·5H₂O; SO, 15 mg/kg copper in CuSO₄·5H₂O + 7.5 mg/kg copper in Cu-proteinate; O1, O2, O3 and O4, 10, 20, 30 and 40 mg/kg copper in the form of Cu-proteinate, respectively. A total of 840 shrimp (5.30 ± 0.04 g) were randomly distributed to 21 tanks (3 tanks/diet, 40 shrimp/tank). An 8-week feeding trial was conducted. The results showed that there was no significant difference in growth performance and whole shrimp chemical compositions among all groups. Compared with inorganic copper, dietary organic copper (O2 and O3) increased total protein, albumin, and glucose content of plasma, while decreased triglyceride and total cholesterol of plasma. Copper concentration in plasma and muscle and gene expression of metallothionein and copper-transporting ATPase 2 like in hepatopancreas were higher in shrimp fed organic copper (SO, O2, O3 and O4). The lowest mortality after low temperature (10 °C) challenge test was observed in the O2 and O3 groups. Organic copper (SO, O2, O3 and O4) significantly enhanced the antioxidant capacity (in terms of higher activities of total superoxide dismutase, copper zinc superoxide dismutase, catalase, glutathione peroxidase and total antioxidant capacity, lower malondialdehyde concentration of plasma, and up-regulated gene expression of superoxide dismutase, copper zinc superoxide dismutase, catalase and glutathione peroxidase of hepatopancreas). Organic copper (SO, O2, O3 and O4) enhanced the immune response (in terms of higher number of total hemocytes, higher activities of acid phosphatase, alkaline phosphatase, phenoloxidase, hemocyanin and lysozyme in plasma, and higher gene expressions of alkaline phosphatase, lysozyme and hemocyanin in hepatopancreas). Inorganic copper (Diet S) also had positive effects on white shrimp compared with the C diet, but the SO, O2, O3 and O4 diets resulted in better results, among which the O2 diet appeared to be the best one. In conclusion, organic copper was more beneficial to shrimp health than copper sulfate.

First report on the burden and distribution of Cu, Zn, Pb, and Cd in the Ocellated icefish (Chionodraco rastrospinosus) of northern Antarctic Peninsula

Understanding the distribution of trace elements in Ocellated icefish (Chionodraco rastrospinosus), one of fish species with lacking hemoglobin from the family Channichthyidae and distributes in a very limited area at the south Scotia Sea, will help understand their physiological composition and conserve this vulnerable population; however, information on this topic is extremely limited. This study examines trace elements (two essential elements, copper [Cu] and zinc [Zn], and two non-essential elements, cadmium [Cd] and lead [Pb]) in C. rastrospinosus and provides for the first time baseline data on elemental distribution in four tissues of C. rastrospinosus in the northern Antarctic Peninsula (NAP). The element concentrations showed the following trends: Zn > Cu > Pb > Cd in muscle and stomach and Zn > Cu > Cd > Pb in intestine and liver. Among all tissues, muscle had the lowest element concentrations. The average Zn level is 70.81 ± 28.91 μg g^-1 dry weight (DW) in C. rastrospinosus muscle, which is higher significantly than average levels of Cu (0.56 ± 0.41 μg g^-1 DW), Pb (0.29 ± 0.33 μg g^-1 DW) and Cd (0.12 ± 0.05 μg g^-1 DW). Zn and Cd concentrations in the stomach and intestines were significantly positively correlated. C. rastrospinosus could be a useful bioindicator for monitoring variability in trace elements dynamics in NAP and the environmental variability in this region.

The Assessment of Dietary Organic Zinc on Zinc Homeostasis, Antioxidant Capacity, Immune Response, Glycolysis and Intestinal Microbiota in White Shrimp (Litopenaeus vannamei Boone, 1931)

This study aimed to assess dietary organic zinc on zinc homeostasis, antioxidant capacity, immune response, glycolysis and intestinal microbiota in white shrimp (Litopenaeus vannamei Boone, 1931). Six experimental diets were formulated: Control, zinc free; S120, 120 mg·kg⁻¹ zinc from ZnSO₄·7H₂O added into control diet; O30, O60, O90 and O120, 30, 60, 90 and 120 mg·kg⁻¹ zinc from Zn-proteinate added into control diet, respectively. The results showed that organic zinc significantly promoted zinc content and gene expression of ZnT1, ZIP11 and MT in the hepatopancreas and enhanced antioxidant capacity and immunity (in terms of increased activities of T-SOD, Cu/Zn SOD, PO, LZM, decreased content of MDA, upregulated expressions of GST, G6PDH, ProPO, LZM and Hemo, and increased resistance to Vibrio parahaemolyticus). Organic zinc significantly upregulated GluT1 expression in the intestine, increased glucose content of plasma and GCK, PFK and PDH activities of hepatopancreas, and decreased pyruvate content of hepatopancreas. Organic zinc improved intestinal microbiota communities, increased the abundance of potentially beneficial bacteria and decreased the abundance of potential pathogens. Inorganic zinc (S120) also had positive effects, but organic zinc (as low as O60) could achieve better effects. Overall, organic zinc had a higher bioavailability and was a more beneficial zinc resource than inorganic zinc in shrimp feeds.

Transgenerational effects of zinc in zebrafish following early life stage exposure

Although toxic effects of zinc (Zn) have been well established in the different developmental stages in fish, long-lasting effects of Zn exposure during embryonic development have not been explored. Exposure to an environmentally relevant Zn concentration of 10 μM (650 μg/L) during the first five days after fertilization did not affect survival, body weight, malformations or overall hatching success of F0 and F1 larvae. Zn exposure did, however, result in delayed hatching in both the F0 and F1 generations and caused significant changes in homeostasis of Zn and selenium (Se) in F0 and F1 fish. This was especially pronounced when F1 embryos from Zn-exposed parents were treated with 30 μM (2000 μg/L) Zn. In the F0 generation, skewed sex ratio towards males and changes in homeostasis of Zn, Se and manganese (Mn) in the brain, gill, liver and gonad of adult fish were also observed. These changes were associated with altered expression of Zn- and Mn-regulatory genes and sex differentiation genes in F0 and F1 fish. The present study suggests that fish may carry memory from embryo-larval Zn exposure into adulthood and further to the next generation. The present study shows that ecotoxicological risk of an exposure to Zn during embryo-larval development may persist long after recovery and may also manifest in the F1 generation.

Integrity and wound healing of rainbow trout intestinal epithelial cell sheets at hypo-, normo-, and hyper-thermic temperatures

How temperature influences fish physiological systems, such as the intestinal barrier, is important for understanding and alleviating the impact of global warming on fish and aquaculture. Monolayers of the rainbow trout cell line, RTgutGC, with or without linear 500 μm wide gaps (wounds) were the in vitro models used to study the integrity and healing of intestinal epithelial sheets at different temperatures. Cultures at hypothermic (4 °C) or hyperthermic (≥ 26 °C) temperatures were compared to normothermic control cultures (18-22 °C). Monolayers remained intact for at least a week at temperatures from 4 to 28 °C, but had lost their integrity after 3 h at 32 °C as the cells pulled away from one another and from the plastic surface. F-actin appeared as prominent stress fibers in cells at 28 °C and as blobs in cells at 32 °C. At normothermia and at 26 °C, cells migrated as sheets into the gaps and closed (healed) the gaps within 5-6 days. By contrast, wounds took 14 days to heal at 4 °C. At 28 °C some cells migrated into the gap in the first few days but mainly as single cells rather than collectively and wounds never healed. When monolayers with wounds were challenged at 32 °C for 3 h and returned to 18-22 °C, cells lost their shape and actin organization and over the next 6 days detached and died. When monolayers were subjected to 26 °C for 24 h and challenged at 32 °C for 3 h prior to being placed at 18-22 °C, cell shape and actin cytoskeleton were maintained, and wounds were healed over 6 days. Thus, intestinal epithelial cells become thermostabilized for shape, cytoskeleton and migration by a prior heat exposure.

Nutrition and Metabolism of Minerals in Fish

Simple Summary

Our aim is to introduce the mineral nutrition of fish and explain the complexity of determining requirements for these elements, which are absorbed and excreted by the fish into the surrounding water. To date, only the requirements for nine minerals have been investigated. The review is focused on the absorption and the dietary factors that reduce their absorption from feed ingredients of plant and animal origin. Some diseases, such as cataracts, anemia and bone deformity, have been linked to dietary deficiency of minerals.

Abstract

Aquatic animals have unique physiological mechanisms to absorb and retain minerals from their diets and water. Research and development in the area of mineral nutrition of farmed fish and crustaceans have been relatively slow and major gaps exist in the knowledge of trace element requirements, physiological functions and bioavailability from feed ingredients. Quantitative dietary requirements have been reported for three macroelements (calcium, phosphorus and magnesium) and six trace minerals (zinc, iron, copper, manganese, iodine and selenium) for selected fish species. Mineral deficiency signs in fish include reduced bone mineralization, anorexia, lens cataracts (zinc), skeletal deformities (phosphorus, magnesium, zinc), fin erosion (copper, zinc), nephrocalcinosis (magnesium deficiency, selenium toxicity), thyroid hyperplasia (iodine), muscular dystrophy (selenium) and hypochromic microcytic anemia (iron). An excessive intake of minerals from either diet or gill uptake causes toxicity and therefore a fine balance between mineral deficiency and toxicity is vital for aquatic organisms to maintain their homeostasis, either through increased absorption or excretion. Release of minerals from uneaten or undigested feed and from urinary excretion can cause eutrophication of natural waters, which requires additional consideration in feed formulation. The current knowledge in mineral nutrition of fish is briefly reviewed.

Role of metal speciation in the exposure medium on the toxicity, bioavailability and bio-reactivity of copper, silver, cadmium and zinc in the rainbow trout gut cell line (RTgutGC)

The role of metal speciation on metal bioavailability, bio-reactivity and toxicity at the fish intestine is poorly understood. To investigate these processes, we used an in vitro model of the rainbow trout (Oncorhynchus mykiss) intestine, the RTgutGC cell line. Cells were exposed to two essential metals (copper and zinc) and two non-essential metals (cadmium and silver) in a medium of well-defined composition, which allowed the determination of metal speciation in solution. Concentrations resulting in a 50% cell viability reduction (EC₅₀) were measured using a viability assay based on two endpoints: metabolic activity and membrane integrity. Metal bioavailability and bio-reactivity was studied at non-toxic (300 nM all metals) and toxic (EC₁₀; Ag-0.6, Cu-0.9, Cd-3, and Zn-9 μM) concentrations. Bioavailability (i.e. intracellular metal accumulation) was determined by ICP-MS, while bio-reactivity (i.e. induction of a metal specific transcriptional response) was determined by measuring the mRNA levels of a known biomarker of metal exposure (i.e. metallothionein) and of copper and zinc transporters (i.e. ATP7A and ZnT1). Dominant metal species in the exposure medium were Zn²⁺, CuHPO₄, CdCl⁺, and AgCl₂^- respectively for Zn, Cu, Cd, and Ag. The EC_50s showed the metal toxicity hierarchy: Ag > Cu > Cd > Zn. In RTgutGC cells, essential metal homeostasis was tightly regulated while non-essential metals accumulated more readily. Non-essential metals were also more bio-reactive inducing higher MT and ZnT1 mRNA levels. Taken together these findings indicate that metal toxicity in RTgutGC cannot solely be explained by extracellular metal speciation but requires the evaluation of metal bioavailability and bio-reactivity.

Zn(ii)-Curcumin supplementation alleviates gut dysbiosis and zinc dyshomeostasis during doxorubicin-induced cardiotoxicity in rats

Doxorubicin is a powerful anticancer agent used to treat a variety of human neoplasms. However, the clinical use of doxorubicin is hampered by cardiotoxicity and effective cardioprotective adjuvants do not exist. Dietary zinc, an essential nutrient, is required to maintain steady-state tissue zinc levels and intestinal homeostasis and may yield therapeutic benefits in diseases associated with zinc dysregulation or gut dysbiosis. Here, we investigated the effects of dietary Zn(ii)-curcumin (ZnCM) solid dispersions on gut dysbiosis and zinc dyshomeostasis during doxorubicin-induced cardiotoxicity in rats. Rats were injected with multiple low doses of doxorubicin and orally administered ZnCM daily over four weeks. Daily administration of ZnCM not only alleviated Dox-induced gut dysbiosis-as indicated by the increased Firmicutes-to-Bacteroidetes ratio and the maintenance of the relative abundances of major beneficial bacteria including Clostridium_XIVa, Clostridium_IV, Roseburia, Butyricicoccus and Akkermansia-but also maintained intestinal barrier integrity and decreased the lipopolysaccharide (LPS) contents of feces and plasma. ZnCM also significantly attenuated doxorubicin-induced zinc dyshomeostasis, which was mirrored by preservation of zinc levels and expression of zinc-related transporters. Furthermore, ZnCM significantly improved heart function and reduced cardiomyocyte apoptosis and myocardial injury in doxorubicin-treated rats. Notably, the regulation of zinc homeostasis and cardioprotective and microbiota-modulating effects of ZnCM were transmissible through horizontal feces transfer from ZnCM-treated rats to normal rats. Thus, ZnCM supplementation has potential as an effective therapeutic strategy to alleviate gut dysbiosis and zinc dyshomeostasis during doxorubicin-induced cardiotoxicity.

Recommendations for dietary level of micro-minerals and vitamin D3 to Atlantic salmon (Salmo salar) parr and post-smolt when fed low fish meal diets

Atlantic salmon (Salmo salar) feeds have changed drastically in their composition from being predominantly marine-based to plant-based. This has altered the dietary supply and availability of micro-nutrients to Atlantic salmon. The impact of graded inclusion levels of a nutrient package (NP) comprising of 25 different micro-nutrients were studied in Atlantic salmon parr in freshwater (Trial 1) and post-smolts in seawater (Trial 2). In brief, the NP was included from 0 to 400%, where 100% corresponded to the recommendation by the National Research Council, 2011. Micro-nutrients, namely Zn, Mn, Se, Cu, Fe, Co, I and vitamin D3 were included in the NP with the objective of (re)evaluating the dietary need to meet the requirement of Atlantic salmon parr and post-smolt, when fed low fish meal, plant ingredient-based diets. Responses in apparent availability coefficient (AAC), whole body and vertebrae mineral concentrations, and retention were analysed. AAC of Cu, Mn, Se and Zn responded in a quadratic fashion with an increase in NP from 0 to 400% in freshwater parr; AAC could not be measured in post-smolt salmon. The whole-body concentration of Zn, Se, Co and I in Atlantic salmon parr were significantly affected by increasing NP inclusion; the same was observed for Zn, Se and Co in post-smolt Atlantic salmon. Vertebrae mineral concentration as the response criterion was non-responsive in parr; whereas, in post-smolt, Co had a linear increase, while Zn and Se showed a non-linear increase upon 0 to 400 NP inclusion. Zinc concentration and activities of alkaline phosphatase (ALP) and tartrate-resistant acid phosphatase (TRAP) in vertebrae indicated increased bone resorption in post-smolt Atlantic salmon; TRAP activity increased linearly with NP inclusion in post-smolt, but not in parr. Significant correlations between Zn and Se were observed in AAC and vertebral concentrations, indicating an interaction in intestinal uptake and vertebral deposition. Overall, Atlantic salmon parr held in freshwater were able to satisfy the requirement for the trace minerals Zn, Mn, Se, Cu, and Fe through supply from 100-150 NP, corresponding to 101-132, 47-63, 0.6-0.8, 12-16 and 150-166 mg kg ^-1, respectively; for iodine, dietary supply from 150-200 NP, corresponding to 0.7-1.6 mg kg^-1, was required. In the seawater, Atlantic salmon post-smolt, in general, required micro-minerals and vitamin D3 levels as supplied through 150-200 NP, corresponding to 140-177, Zn; 61-67, Mn; 0.9-1, Se; 14-16, Cu; and vitamin D3, 0.06-0.09 mg kg ^-1 to fulfil the requirement, except for Cu which was satisfied at 100-150 NP, equivalent to 13-14 mg kg ^-1 diet.