Inorganic, organic, and encapsulated minerals in vegetable meal based diets for Sparus aurata (Linnaeus, 1758)

Zinc-L-Selenomethionine Improves Growth and Hemato-Biochemical Parameters at Low but not at High Stocking Density for Nile Tilapia Males

The study aimed to examine the interaction between diets supplemented with zinc-L-selenomethionine (ZnSeMet) and two stocking densities (SD) on Nile tilapia (Oreochromis niloticus) males. Four extruded diets were formulated: 0.0, 0.5, 1.0, and 2.0 mg ZnSeMet kg-1. Fish (58.00 g) were reared at a low SD (LSD) (15 fish tank-1 or 4,35 kg m-3) and a high SD (HSD) (45 fish tank-1 or 13,05 kg m-3). They were randomly distributed in eight treatments in triplicate in a recirculatory aquaculture system (200 L) and were fed until apparent satiation thrice daily for 65 days. The interaction between LSD and 1.0 or 2.0 mg ZnSeMet kg-1 was better than other treatments for final weight (116.50-174.83 vs. 97.33-139.17 g), weight gain (108.83.50-116.83 vs. 39.00-80.83 g), relative weight gain (188.03-201.18 vs. 66.25-139.40%), total final length (20.12-20.63 vs. 17.33-19.00 cm), specific growth rate (1.76-1.83 vs. 0.85-1.45% day-1) (p < 0.05). In general, the interaction between LSD and 1.0 mg ZnSeMet kg-1 compared to several treatments, showed an increase in plasma total protein (3.23 vs. 2.67-2.78 g dL-1) and total cholesterol (93.67 vs. 68.50-76.67 mg dL-1) levels and a reduction in aspartate aminotransferase activity (14.83 vs. 145.67-155.17 U L-1) (p < 0.05). The highest values for albumin (0.83 vs. 0.57 g dL-1), glucose (56.00 vs. 45.09 mg dL-1), and triglycerides (122.33 vs. 68.87 mg dL-1) in the plasma, erythrocytes (2.22 vs. 2.13 × 106 µL-1), hemoglobin (9.82 vs. 9.26 g dL-1), and hematocrit (33.09 vs. 30.21%) were observed in LSD than HSD-reared fish (p < 0.05). In conclusion, adding 1.0 mg ZnSeMet kg-1 at LSD improved fish growth and hemato-biochemical parameters, but it was not effective at HSD.

Metal-amino acid complexes (Zn, Se, Cu, Fe, and Mn) enhance immune response, antioxidant capacity, liver function enzymes, and expression of cytokine genes in Nile Tilapia reared under field conditions

OBJECTIVES

In the present study, we investigated the effects of partial or total replacement of dietary inorganic trace materials (ITM) with metal-amino acid complexes (MAACs) on immune response, antioxidant capacity, cytokine genes expression, and overall health status of Nile Tilapia Oreochromis niloticus reared in in-pond hapas (mesh cages) under field conditions.

METHODS

All-male Nile Tilapia with an average initial weight of about 90 g fish-1 were stocked into the hapas, in quadruplicates, at a density of 60 fish per hapa (30 fish m-3 ). The fish in each hapa were acclimatized to culture conditions and test diets for 1 week. Water quality parameters, including temperature (°C), pH, dissolved oxygen (mg L-1 ), and total ammonia (mg L-1 ), were monitored regularly. The MAACs were formulated to contain the same mineral concentrations found in the inorganic premix. Metal-amino acid complexes replaced the ITM premix at 0 (control), 25, 50, 75, and 100% levels (Table 1). The diets were fed to caged Nile Tilapia twice a day, for 80 days, at a daily rate of 3% of their body weights. The fish were weighed every 10 days, and the daily rations were readjusted. At harvest, fish in each hapa were collected, counted, and weighed collectively. Five fish from each hapa were rapidly anesthetized, and used for chemical and physiological analyses, including antioxidant and immune response analyses, liver function analysis, and gene expression.

RESULT

The activities of lysozyme, respiratory burst (%), alternative complement (ACH50), phagocytic cells, phenoloxidase, superoxide dismutase, glutathione peroxidase, and liver function enzymes were all improved with increasing supplemental MAACs up to the 50% substitution level. The expression of cytokine genes, including interferon, tumor necrosis factor, interleukin-1, serum alkaline phosphatase, the integrated microbial genomes, chloramphenicol acetyltransferase, and transforming growth factor genes, was significantly upregulated in fish fed on MAAC-supplemented diets compared with the control group. The 50% MAAC level produced the highest upregulation of these genes, whereas gene expression decreased with increasing dietary MAAC levels to 75% and 100%. The quadratic regression analysis indicated that about 60-65% MAAC is required for maximum promotion of immunological and oxidative stress responses, gene expression, and overall health status of Nile Tilapia reared in in-pond hapas under field conditions.

CONCLUSION

Replacement of the ITM premix with a MAAC premix enhanced the immune and antioxidant responses of Nile Tilapia.

Effect of Dietary Inorganic and Chelated Trace Mineral Supplementation on the Growth Performance and Skeletal Deformities of European Seabass and Senegalese Sole Post-larvae

Trace elements such as Cu, Fe, Mn and Zn are essential minerals in fish diets, especially important at early larval stages. The chemical speciation of these elements directly influences their uptake efficiency and metabolic utilization. In order to optimize the form of trace elements incorporated into larval feed, two experiments were conducted using two commercial fish species, European seabass (Dicentrarchus labrax) and Senegalese sole (Solea senegalensis), and two chemical forms (inorganic and glycinate chelates). Several fish performance parameters were measured, as well as bone status parameters to assess which form of mineral results in optimal fish biological performance. European seabass and Senegalese sole post-larvae were unresponsive (P > 0.05) to dietary treatments in terms of dry weight (DW), standard length (SL), relative growth rate (RGR) or feed conversion rates (FCR) when fed diets supplemented with chelated over inorganic trace minerals. This study suggests that replacing dietary inorganic mineral supplementation by their organic glycinate-chelated forms brings no beneficial effects on somatic growth and bone development in Senegalese sole and European seabass post-larvae fed high-quality commercial microdiets. Additionally, we show that mineral leaching from diets can be significant, but the use of chelated minerals can potentially mitigate this leaching phenomenon. Therefore, the selection of the dietary mineral form should take into account not only their economic value, but also their biological effect and environmental impact. Data generated in this trial provides new knowledge in trace mineral nutrition of early-stage marine fish.

Optimisation of trace mineral supplementation in diets for Atlantic salmon smolt with reference to holistic fish performance in terms of growth, health, welfare, and potential environmental impacts

The aquafeed ingredient inventory is ever changing, from marine to plant based, and recently evolving to incorporate increasing amounts of low trophic, side stream and circular economy based raw materials, each one contributing with variable amounts and qualities of macro- and micronutrients. Meeting the micronutrient requirement of farmed fish for healthy and efficient growth under normal and challenging conditions is of paramount importance. In this study we run a trial based on a 2 × 4 factorial design with three replications for each dietary treatment, where Atlantic salmon smolt were fed one of 8 experimental diets supplemented with either organic or inorganic mineral premixes (copper, iron, manganese, selenium, and zinc) at four dietary inclusion levels. We saw a trend for higher growth rate in the organic mineral groups irrespective of the dietary mineral levels. Mineral digestibility was negatively correlated with increasing mineral supplementation levels for all tested minerals but Se which increased with the increasing supplementation in the inorganic and up to the 2nd inclusion level in the organic mineral groups. Increasing mineral supplementation affected retention efficiency of Zn, Mn, Cu and Fe while mineral source affected only the retention of Se which was higher in the organic mineral groups. Moreover, fish obtained higher EPA and DHA in their body and increased slaughter yield in the organic as compared to the inorganic mineral groups and corroborated that trace mineral inclusion levels play a key role on salmon fillet's technical quality. More effects from different origin and dietary inclusion levels of trace minerals were seen on fillet yield, fillet technical and nutritional quality, bone strength, skin morphology, organ mineralization and midgut transcriptome.

Categorising cheetah behaviour using tri-axial accelerometer data loggers: a comparison of model resolution and data logger performance

BACKGROUND

Extinction is one of the greatest threats to the living world, endangering organisms globally, advancing conservation to the forefront of species research. To maximise the efficacy of conservation efforts, understanding the ecological, physiological, and behavioural requirements of vulnerable species is vital. Technological advances, particularly in remote sensing, enable researchers to continuously monitor movement and behaviours of multiple individuals simultaneously with minimal human intervention. Cheetahs, Acinonyx jubatus, constitute a "vulnerable" species for which only coarse behaviours have been elucidated. The aims of this study were to use animal-attached accelerometers to (1) determine fine-scale behaviours in cheetahs, (2) compare the performances of different devices in behaviour categorisation, and (3) provide a behavioural categorisation framework.

METHODS

Two different accelerometer devices (CEFAS, frequency: 30 Hz, maximum capacity: ~ 2 g; GCDC, frequency: 50 Hz, maximum capacity: ~ 8 g) were mounted onto collars, fitted to five individual captive cheetahs. The cheetahs chased a lure around a track, during which time their behaviours were videoed. Accelerometer data were temporally aligned with corresponding video footage and labelled with one of 17 behaviours. Six separate random forest models were run (three per device type) to determine the categorisation accuracy for behaviours at a fine, medium, and coarse resolution.

RESULTS

Fine- and medium-scale models had an overall categorisation accuracy of 83-86% and 84-88% respectively. Non-locomotory behaviours were best categorised on both loggers with GCDC outperforming CEFAS devices overall. On a coarse scale, both devices performed well when categorising activity (86.9% (CEFAS) vs. 89.3% (GCDC) accuracy) and inactivity (95.5% (CEFAS) vs. 95.0% (GCDC) accuracy). This study defined cheetah behaviour beyond three categories and accurately determined stalking behaviours by remote sensing. We also show that device specification and configuration may affect categorisation accuracy, so we recommend deploying several different loggers simultaneously on the same individual.

CONCLUSION

The results of this study will be useful in determining wild cheetah behaviour. The methods used here allowed broad-scale (active/inactive) as well as fine-scale (e.g. stalking) behaviours to be categorised remotely. These findings and methodological approaches will be useful in monitoring the behaviour of wild cheetahs and other species of conservation interest.

Organic Selenium (OH-MetSe) Effect on Whole Body Fatty Acids and Mx Gene Expression against Viral Infection in Gilthead Seabream (Sparus aurata) Juveniles

The supplementation of fish diets with OH-SeMet reduces oxidative stress and modulates immune response against bacterial infection. However, despite the importance of essential polyunsaturated fatty acids in fish nutrition and their high risk of oxidation, the potential protective effect of OH-SeMet on these essential fatty acids has not been studied in detail. Moreover, while viral infection is very relevant in seabream production, no studies have focused the Se effects against viral infection. The aim of the present study was to assess the impact of dietary supplementation with OH-SeMet on gilthead seabream fatty acid profiles, growth performance and response against viral infection. Gilthead seabream juveniles (21.73 ± 0.27 g) were fed for 91 days with three experimental diets, a control diet without supplementation of Se (0.29 mg Se kg diet-1) and two diets supplemented with OH-SeMet (0.52 and 0.79 mg Se kg diet-1). A crowding stress test was performed at week 7 and an anti-viral response challenge were conducted at the end of the feeding trial. Selenium, proximate and fatty acid composition of diets and body tissues were analyzed. Although fish growth was not affected, elevation in dietary Se proportionally raised Se content in body tissues, increased lipid content in the whole body and promoted retention and synthesis of n-3 polyunsaturated fatty acids. Specifically, a net production of DHA was observed in those fish fed diets with a higher Se content. Additionally, both monounsaturated and saturated fatty acids were significantly reduced by the increase in dietary Se. Despite the elevation of dietary Se to 0.79 mg kg-1 not affecting basal cortisol levels, 2 h post-stress plasma cortisol levels were markedly increased. Finally, at 24 h post-stimulation, dietary OH-SeMet supplementation significantly increased the expression of the antiviral response myxovirus protein gene, showing, for the first time in gilthead seabream, the importance of dietary Se levels on antiviral defense.

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.

Effect of Trace Minerals and B Vitamins on the Proliferation/Cytotoxicity and Mineralization of a Gilthead Seabream Bone-Derived Cell Line

Trace minerals and vitamins are known modulators of bone metabolism, and dietary optimization of these components may improve skeletal development and reduce the occurrence of skeleton deformities in farmed fish. As for larval stages, mineral and water-soluble vitamin nutrition requirements are lacking in research efforts and knowledge is scarce. An in vitro cell system developed from gilthead seabream vertebra and capable of mineralization was used to assess the effect of B vitamins (thiamin and pyridoxine) and trace minerals (copper, manganese, and zinc in a sulfated and chelated form) on cell proliferation and extracellular matrix (ECM) mineralization. Dependent on dose, inhibition of cellular proliferation and/or cytotoxic effects was observed for all nutrients tested and LD₅₀ values were determined: copper, 67.4-69.5 ppm; manganese, 20.9-29.8 ppm; zinc, 37.1-42.8 ppm in sulfated and chelated form respectively; thiamin, 6273 ppm; pyridoxine, 14226 ppm. ECM mineralization was enhanced by mineral (dose and form dependent) and vitamin (dose dependent) supplementation, at non-toxic concentrations below the determined LD_50s. This in vitro work confirmed the mineralogenic action of trace minerals and water-soluble vitamins and provided valuable insights for subsequent in vivo nutritional trials.

Effects of Schizochytrium and micro-minerals on immune, antioxidant, inflammatory and lipid-metabolism status of Micropterus salmoides fed high- and low-fishmeal diets

A 12-week factorial experiment was conducted to investigate the interactive effects of dietary algal meal (Schizochytrium sp., AM) and micro-minerals (MM, either organic [OM] or inorganic [IM]) on the immune and antioxidant status, and the expression of hepatic genes involved in the regulation of antioxidants, inflammatory cytokines, lipid metabolism, and organ growth of largemouth bass (LMB; Micropterus salmoides) fed high-and low-fishmeal (FM) diets. For this purpose, two sets of six iso-nitrogenous (42% crude protein) and iso-lipidic (12% lipid) diets, such as high (35%) and low (10%) FM diets were formulated. Within each FM level, AM was used to replace 50% or 100% of fish oil (FO), or without AM (FO control) and supplemented with either OM or IM (Fe, Zn, Mn, Cu, and Se). Diets were fed to juvenile LMB (initial weight, 25.87 ± 0.08 g) to near satiation twice daily. The results indicated that FO replacement by dietary AM did not change the levels of most biochemical (ALB, AMY, TP and GLOB), antioxidants (SOD, GPx and GSH), and immune (IgM and lysozyme) parameters in LMB, except ALP and CAT. MM affected only hepatic GSH, with lower values in fish fed the OM diets. FM influenced the levels of ALP, AMY, GLOB, IgM, and MDA (P < 0.05). A three-way interactive effect (P = 0.016) was found on IgM only, with lower levels in fish fed diet 12 (low-FM, AM100, OM). Subsequently, the relative expressions of hepatic antioxidants (Cu/Zn-SOD and GPx-4), inflammatory cytokines (TNF-α and TGF-β1), lipid metabolism (FASN and CYP7A1), and organ growth (IGF-I) related genes were affected by the dietary treatments, with interactions being present in Cu/Zn-SOD, TNF-α, TGF-β1, FASN and IGF-I. Overall, dietary AM could be used as an alternative to FO in low-FM diets without compromising the health of LMB, especially when it is supplemented with MM.

In vitro digestion method to evaluate solubility of dietary zinc, selenium and manganese in salmonid diets

BACKGROUND

The determination of dietary mineral solubility is one of the main steps in the evaluation of their availability for a given species.

METHODS

This study proposed an in vitro digestion method (acidic and alkaline hydrolysis). The method was applied to evaluate the solubility of inorganic and organic forms of zinc (Zn), selenium (Se) and manganese (Mn) in salmonid diets. An inorganic mineral (IM) diet was supplemented with zinc sulphate, sodium selenite and manganous sulphate and an organic mineral (OM) diet was supplemented with zinc chelate of glycine, l-selenomethionine and manganese chelate of glycine.

RESULTS

The solubility of Zn was similar in both diets tested. The amount of soluble Zn was low in the acidic hydrolysis (3-8%) and lower in the alkaline hydrolysis (0.4-2%). The solubility of Se was higher in the OM diet (7-34%) compared with the IM diet (3-12%). Regarding Mn, after the acidic hydrolysis the solubility was higher in the IM diet (6-25%) than the OM diet (4-17%). The in vitro solubility were compared with in vivo availability of Zn, Se and Mn. Data obtained for solubility (%) of Zn, Se and Mn was lower when compared with apparent availability (%) of Zn, Se and Mn.

CONCLUSION

Data obtained demonstrated that solubility of Zn, Se and Mn was influenced by the mineral chemical form supplemented to the diet and by the gastrointestinal environment. The solubility of Zn, Se and Mn was not comparable with the apparent availability of Zn, Se and Mn. Nevertheless, the effect of the chemical form of the minerals was similar for the solubility of Zn, Se and Mn and the apparent availability of Zn, Se and Mn. Considering the overall results of this study, the in vitro method could replace some of the in vivo studies for a qualitative evaluation but not for a quantitative evaluation.

Skin Mucus Fatty Acid Composition of Gilthead Sea Bream (Sparus Aurata): A Descriptive Study in Fish Fed Low and High Fish Meal Diets

Terrestrial protein and lipid sources are commonly used as substitutes for marine fishery-derived raw ingredients in fish diets. However, their use is related with several side-effects on marine fish performance, health, or disease resistance. Physical barriers of the skin, gills, and gut constitute the primary defense mechanism of fish. Skin mucus mucosal mucins, water, proteins, ions, and lipids determine the physical, chemical, and protective characteristics of skin mucus. Very little is known about the influence of diet composition on fish skin mucus fatty acid profile. Gilthead sea bream skin mucus contained 10% of total lipids (TL), which consisted of 50–60% neutral (NL) and 40–50% polar lipids (PL) fractions. Σn−3 long chain polyunsaturated fatty acids (LC-PUFA) deposition was preferential in the NL fraction, whereas Σn−6LC-PUFA accumulation was similar in both lipid classes. Docosahexaenoic acid (DHA; 22:6n−3) was the main LC-PUFA stored in skin mucus (14% TL) in relation to eicosapentaenoic acid (EPA; 20:5n−3) (2–3% TL) and arachidonic acid (ARA; 20:4n−6) (2% TL). This study denotes the importance of DHA as component of skin mucus lipids compared to other essential fatty acids, such as EPA and ARA, as well as importance of maintaining an adequate Σn−3/ Σn−6 ratio, regardless of dietary intake.

Speciation of zinc in fish feed by size exclusion chromatography coupled to inductively coupled plasma mass spectrometry - using fractional factorial design for method optimisation and mild extraction conditions

Zinc (Zn) is an element essential to all living organisms and it has an important role as a cofactor of several enzymes. In fish, Zn deficiency has been associated with impaired growth, cataracts, skeletal abnormalities and reduced activity of various Zn metalloenzymes. Fish meal and fish oil traditionally used in salmon feed preparation are being replaced by plant-based ingredients. Zinc additives are supplemented to salmon feed to ensure adequate Zn levels, promoting good health and welfare in Atlantic salmon (Salmo salar). The main objective of the present study was to evaluate Zn species found in an Atlantic salmon feed. This work describes a Zn extraction method that was optimized using a fractional factorial design (FFD), whereby the effect of six factors could be studied by performing only eight experiments. The effects of the type of extraction solution and its molar concentration, pH, presence of sodium dodecyl sulphate, temperature and extraction time on Zn extraction were investigated. Mild extraction conditions were chosen in order to keep the Zn species intact. Total Zn (soluble fractions and non-soluble fractions) was determined by inductively coupled plasma mass spectrometry (ICP-MS). The highest Zn recovery was obtained using 100 mM Tris-HCl, pH 8.5 at a temperature of 4 °C for 24 h where the total Zn in soluble fraction and non-soluble fraction was 9.9 ± 0.2% and 98 ± 6%, respectively. Zinc speciation analysis (on the soluble fractions) was further conducted by size exclusion inductively coupled plasma mass spectroscopy (SEC-ICP-MS). The SEC-ICP-MS method provided qualitative and semi-quantitative information regarding Zn species present in the soluble fractions of the feed. Four Zn-containing peaks were found, each with different molecular weights: Peak 1 (high molecular weight - ≥600 kDa), peak 2 and peak 3 (medium molecular weight - 32 to 17 kDa) were the least abundant (1-6%), while peak 4 (low molecular weight - 17 to 1.36 kDa) was the most abundant (84-95%).