Effects of different levels of dietary zinc on the gilthead,Sparus aurata during the growing season
TL;DR: The hypothesis that zinc in the CNS should be strictly controlled in order to maintain the functional role of the metal is reinforced, as significant differences in tissue zinc concentrations were obtained between fish fed different amounts of zinc.
Abstract: Gilthead were fed three diets. Diet A was the control diet, whereas diets B and C were supplemented with 300 and 900 mg Zn/kg, respectively. Fish fed with diet C, at the end of the experiment, showed the lowest weight. Zinc concentrations presented the higher values in gills, liver, and kidney. Muscle and brain had the lower mean values and showed a tight control of zinc levels. These results reinforce the hypothesis that zinc in the CNS should be strictly controlled in order to maintain the functional role of the metal. Significant differences in tissue zinc concentrations were obtained between fish fed different amounts of zinc, the metal concentrations being higher in tissues of fish fed diet C. The tissue decrease of zinc, found at the end of the experiment, may depend on a lower feed consumption or on different zinc requirements during the cold season. These changes, even if not univocal among the three diets, may be associated with the life cycle of fish. Furthermore, copper concentrations were little affected by the different concentrations of zinc in the three diets; liver and kidney presented the highest concentrations; liver showed a significant decrease in copper content at the end of the experiment. We conclude that: zinc concentrations of the diet may affect the gilthead weights and the tissual metal content; and zinc concentrations in the diets, depending on the growth rate, may be varied depending on the season.
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TL;DR: It is found that dietborne Zn toxicity has not yet been demonstrated in rainbow trout or turbot probably because these species have been exposed to relatively low doses of metal and effects on growth and reproduction have not been analyzed.
Abstract: To date, most researchers have used dietborne metal concentrations rather than daily doses to define metal exposure and this has resulted in contradictory data within and between fish species. It has also resulted in the impression that high concentrations of dietborne Cu and Zn (e.g. > 900 mg kg(-1) dry diet) are relatively non-toxic to fish. We re-analyzed existing data using rations and dietborne metal concentrations and used daily dose, species and life stage to define the toxicity of dietborne Cu and Zn to fish. Partly because of insufficient information we were unable to find consistent relationships between metal toxicity in laboratory-prepared diets and any other factor including, supplemented metal compound (e.g. CuSO(4) or CuCl(2)), duration of metal exposure, diet type (i.e. practical, purified or live diets), or water quality (flow rates, temperature, hardness, pH, alkalinity). For laboratory-prepared diets, dietborne Cu toxicity occurred at daily doses of > 1 mg kg(-1) body weight d(-1) for channel catfish (Ictalurus punctatus), 1-15 mg kg(-1) body weight d(-1) (depending on life stage) for Atlantic salmon (Salmo salar) and 35-45 mg kg(-1) body weight d(-1) for rainbow trout (Oncorhynchus mykiss). We found that dietborne Zn toxicity has not yet been demonstrated in rainbow trout or turbot (Scophthalmus maximus) probably because these species have been exposed to relatively low doses of metal ( < 90 mg kg(-1) body weight d(-1)) and effects on growth and reproduction have not been analyzed. However, daily doses of 9-12 mg Zn kg(-1) body weight d(-1) in laboratory-prepared diets were toxic to three other species, carp Cyprinus carpio, Nile tilapia Oreochromis niloticus, and guppy Poecilia reticulata. Limited research indicates that biological incorporation of Cu or Zn into a natural diet can either increase or decrease metal bioavailability, and the relationship between bioavailability and toxicity remains unclear. We have resolved the contradictory data surrounding the effect of organic chelation on metal bioavailability. Increased bioavailability of dietborne Cu and Zn is detectable when the metal is both organically chelated and provided in very low daily doses. We have summarized the information available on the effect of phosphates, phytate and calcium on dietborne Zn bioavailability. We also explored a rationale to understand the relative importance of exposure to waterborne or dietborne Cu and Zn with a view to finding an approach useful to regulatory agencies. Contrary to popular belief, the relative efficiency of Cu uptake from water and diet is very similar when daily doses are compared rather than Cu concentrations in each media. The ratio of dietborne dose:waterborne dose is a good discriminator of the relative importance of exposure to dietborne or waterborne Zn. We discuss gaps in existing data, suggest improvements for experimental design, and indicate directions for future research.
331 citations
TL;DR: In this article, a meta-analysis of literature data on mineral and trace element requirements of fish was performed with the major objectives of identifying appropriate response criteria and the factors affecting the minimal dietary inclusion levels.
Abstract: Meta-analysis of literature data on mineral and trace element requirements of fish was performed with the major objectives of identifying appropriate response criteria and the factors affecting the minimal dietary inclusion levels. The primary data set included 25 studies on available P, 20 on Ca, 24 on Mg, 5 on K, 37 for Zn, 23 for Se, 19 for Mn, 16 for Fe and 13 for Cu. Broken line regression analysis with linear plateau model (P, Ca, Mg and K) or two-linear line model (Zn, Cu, Fe, Mn and Se) was used for determining the minimal dietary inclusion levels. Vertebral mineral concentration (P, Ca, Zn and Mn), whole-body mineral levels (Mg, K and Fe) and hepatic enzyme activity (Se) were found to be the most appropriate criteria for the respective minerals analysed. In general, weight gain as the criterion resulted in a lower estimate (by 18–42%) than those obtained using whole-body or vertebral mineral concentrations as response criteria. The analysis also showed that different fish species do not show large variations in the mineral and trace element concentrations in the whole body and tissues. Factors such as species group and digestive physiology, type of experimental diet used and dietary interactions, type of mineral source and mineral concentration of water were found to affect the minimal dietary inclusion levels of certain minerals. Besides the meta-analysis, research needs in mineral nutrition of fish with reference to growing changes in dietary strategies and rearing systems are discussed.
206 citations
TL;DR: The results suggested that trace metals' enrichment in the sediments may be attributed to the fish farm effluents, although metal concentrations are not likely to cause harmful effects in the marine ecosystem.
99 citations
TL;DR: The study showed the need to supplement seabream with early weaning diets based on squid meal and krill oil with one or more of the antioxidant minerals, to promote larval growth, bone mineralization and prevention of skeleton anomalies, organic minerals being more effective than inorganic forms and nanometals in promoting Mineralization and stress resistance.
Abstract: Levels of the oxidative stress-related minerals selenium (Se), zinc (Zn) and manganese (Mn) that should be supplied in microdiets for marine fish larvae depend on the availability of the molecular form of these minerals. The objective of this study was to determine how effectively Se, Zn and Mn in organic, inorganic and nanoparticle forms promote larval performance and bone development. Microdiets supplemented with Se, Zn and Mn were fed for 24 days to 20 dah seabream larvae. Microdiets without Se, Zn and Mn supplementation were associated with poor growth, low bone mineralization and a high incidence of anomalies in the branchial arches. Including Zn, Mn and Se in an amino acid chelate organic form promoted maximum larval growth, increased body lipid reserves, enhanced early mineralization and prevented branchial arches anomalies. In contrast, feeding with inorganic forms of these minerals was less effective than organic minerals in improving larval weight or bone mineralization in comparison to the non-supplemented diet. Moreover, the larvae were less resistant to stress, and fish showed higher bone anomalies in the pre-hemal region. Adding Zn, Mn and Se in the form of nanometals did not enhance growth, but improved stress resistance and bone mineralization. The study showed the need to supplement seabream with early weaning diets based on squid meal and krill oil with one or more of the antioxidant minerals, to promote larval growth, bone mineralization and prevention of skeleton anomalies, organic minerals being more effective than inorganic forms and nanometals in promoting mineralization and stress resistance.
56 citations
TL;DR: It is concluded that the different environmental conditions, experienced by wild and farmed fish, have significantly influenced the biochemical composition of their lateral muscle.
Abstract: Red and white muscle from specimens of wild and farmed gilthead sea bream (Sparus aurata) were analyzed for histochemical ATPase activity, total protein content, fatty acids, trace element concentrations and myosin isoforms. The fibre type composition of muscle samples was confirmed histochemically by the ATPase reaction, which did not show any differences between the two groups of animals. Myosin ATPase activities, myosin and protein yields were significantly higher in white muscle than in the red muscle and for the red muscle the latter two parameters were higher in wild fish. Fatty acid profiles revealed differences between the two groups of animals, probably because of the fatty acid composition of the diets. Zinc, copper and iron concentrations were higher in red muscle than in white muscle; muscles from wild fish were significantly richer in trace elements. No separation of fast and slow heavy chains of myosin could be obtained on SDS-gel electrophoresis, but two dimensional electrophoresis revealed the presence of three light chains in white muscle (LC1F, LC2F, LC3F), and two main types in red muscle (LC1S, LC2S). Small, variable percentages of LC3F were found in the red muscle samples, especially in the wild fish. It is concluded that the different environmental conditions, experienced by wild and farmed fish, have significantly influenced the biochemical composition of their lateral muscle.
50 citations
References
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TL;DR: Majors topics addressed in this review on zinc physiology are chemistry and biochemistry; interface of biochemistry and physiology of zinc; physiology and cell and molecular biology; and pathology.
Abstract: Majors topics addressed in this review on zinc physiology are ; 1) chemistry and biochemistry; 2) interface of biochemistry and physiology of zinc; 3) physiology and cell and molecular biology; 4) pathology
2,850 citations
TL;DR: The study implies that zinc modulates synaptic transmission in the immature hippocampus, a finding that may have implications for understanding benign postnatal seizures in young children suffering with acute zinc deficiency18.
Abstract: The mammalian central nervous system (CNS) contains an abundance of the transition metal zinc, which is highly localized in the neuronal parenchyma. Zinc is actively taken up and stored in synaptic vesicles in nerve terminals, and stimulation of nerve fibre tracts that contain large amounts of zinc, such as the hippocampal mossy fibre system, can induce its release, suggesting that it may act as a neuromodulator. The known interaction of zinc with the major excitatory and inhibitory amino-acid neurotransmitter receptors in the CNS supports this notion. That zinc has a role in CNS synaptic transmission, however, has so far not been shown. Here we report a physiological role for zinc in the young rat hippocampus (postnatal, P3-P14 days). Our results indicate that naturally occurring spontaneous giant depolarizing synaptic potentials (GDPs) in young CA3 pyramidal neurones, mediated by the release of GABA (gamma-aminobutyric acid), are induced by endogenously released zinc. These synaptic potentials are inhibited by specific zinc-chelating agents. GDPs are apparently generated by an inhibitory action of zinc on both pre- and postsynaptic GABAB receptors in the hippocampus. Our study implies that zinc modulates synaptic transmission in the immature hippocampus, a finding that may have implications for understanding benign postnatal seizures in young children suffering with acute zinc deficiency.
384 citations
"Effects of different levels of diet..." refers background in this paper
...A physiological role for endogenous zinc in rat hippocampal synaptic neurotransmission was shown ( 21 )....
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TL;DR: Examination of a group of rainbow trout found that their elemental composition was determined by fish size, stage of life cycle (prefeeding, juvenile, post-juvenile), and reproductive state.
Abstract: By examining a group of rainbow trout (Salmo gairdneri) over their life cycle (ova to 1500 g), 1 found that their elemental composition was determined by fish size, stage of life cycle (prefeeding,...
184 citations
"Effects of different levels of diet..." refers background in this paper
...(22) found a decline in muscle trace elements owing to dilution by growth, whereas concentrations of zinc and copper in the muscle of rainbow trout remained constant despite increasing fish weight (23)....
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TL;DR: It is demonstrated that zinc is an essential trace element in the diet of rainbow trout, even though rearing water contains a low concentration of this element.
Abstract: The requirement of rainbow trout for dietary zinc was investigated by feeding them with diets containing graded levels of zinc. The results of the present study demonstrate that zinc is an essential trace element in the diet of rainbow trout, even though rearing water contains a low concentration of this element (11μg/ι). The fish fed a diet low in zinc content (lppm) showed an extremely low growth rate and high mortality. A large number of the fish on the zinc-deficient diet were found to suffer from cataracts in the eyes and erosion of the fins and of the skin. The dietary zinc levels also influenced the digestibility of protein and carbohydrate, especially that of protein. The proximate composition of the fish body and the contents of trace elements in the various organs varied according to the dietary zinc levels. Judging from the growth rate of the fish, an adequate zinc content of the diet of rainbow trout was estimated to be 15 to 30ppm.
170 citations
"Effects of different levels of diet..." refers background in this paper
...In rainbow trout, judging from the growth rate, an adequate zinc content of the diet was estimated to be 15-30 mg Zn/kg (4)....
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...In addition, no general deficiency signs, such as growth retardation, or specific deficiency signs, such as cataracts (4), appeared in fish fed diet A....
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TL;DR: Groups of rainbow trout (Salmo gairdneri) were fed casein–gelatin diets supplemented with calcium phosphate (Ca3(PO4)2) to produce dietary calcium and phosphorus levels of 1,2, or 4% and 0.9,1.5, o...
Abstract: Groups of rainbow trout (Salmo gairdneri) were fed casein–gelatin diets supplemented with calcium phosphate (Ca3(PO4)2) to produce dietary calcium and phosphorus levels of 1,2, or 4% and 0.9,1.5, o...
147 citations
"Effects of different levels of diet..." refers background in this paper
...However, the dietary level required to prevent the effects of compounds that reduce the bioavailability of zinc is higher (5)....
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