Bioavailability of co-supplemented organic and inorganic zinc and selenium sources in a white...

O R I G I N A L A R T I C L E

Bioavailability of co-supplemented organic and inorganic zincand selenium sources in a white fishmeal-based rainbow trout(Oncorhynchus mykiss) dietS. A. Rider1, S. J. Davies1, A. N. Jha1, R. Clough1 and J. W. Sweetman2

1 School of Biological Sciences, The University of Plymouth, Plymouth, Devon, UK, and

2 John W. Sweetman, Ecomarine Ltd, Samoli, Lixouri, Cephalonia, Greece

Introduction

Dietary zinc (Zn) and selenium (Se) are both essen-

tial elements for metabolic processes and can be

supplemented to meet dietary requirements for fish.

In rainbow trout (Oncorhynchus mykiss), minimum

requirements for Zn (15–30 mg/kg Ogino and Yang,

1978) and Se (0.35 mg/kg Hilton et al., 1980) have

Keywords

rainbow trout, selenium, zinc, bioavailability,

organic, digestibility

Correspondence

Sebastien A. Rider, School of Biological

Sciences, The University of Plymouth,

Plymouth, Devon, UK. Tel: +44 (0) 1752 232

900; Fax: +44 (0) 1752 232 970;

E-mail: [email protected]

Received: 14 February 2008;

accepted: 29 September 2008

First published online: 31 March 2009

Summary

The bioavailability of trace elements in fishmeal diets is influenced by

their chemical forms and dietary anti-nutritional factors. In formulated

fish feed, supplemented organically bound minerals may be more bio-

available than inorganic minerals. A 10-week feeding trial was under-

taken with rainbow trout (Oncorhynchus mykiss) to determine whether

the inclusion of organically bound selenium (Se) and zinc (Zn)

improved uptake and assimilation of these elements compared to com-

monly used inorganic forms. The three diets tested included a control

diet, no added Zn or Se; an organic Se-yeast and Zn-proteinate supple-

mented diet; and an inorganic sodium selenite and Zn-sulphate supple-

mented diet. The endpoints tested were apparent digestibility, whole

body levels, tissue distribution and Se- and Zn-dependent enzyme activi-

ties. Digestibility of residual Se in the basal diet was 54.2 ± 1.0% and

supplemented Se-yeast was significantly more digestible than selenite

(p < 0.05). Digestibility of residual Zn was 21.9 ± 2.0% and no signifi-

cant difference was found between the treatments (p = 0.89). Whole

body Se was raised by both Se sources and to a greatest extent by Se-

yeast (p < 0.001). Zn-sulphate, and to a lesser extent Zn-proteinate,

both raised whole body Zn (p < 0.05). Dietary Zn in the basal diet was

found to be above requirements, yet Zn-sulphate had a significantly

greater retention than Zn-proteinate in those tissues that responded to

Zn supplementation. Se-yeast significantly raised Se in all tissues to a

greater extent than selenite, except in the pyloric caeca and liver where

the greatest increases were by selenite. Only Se-yeast elevated

Se-dependent thioredoxin reductase activity (p < 0.05) and neither

forms of Se affected glutathione peroxidise activity (p = 0.059). Alkaline

phosphatase and carboxypeptidase B were not affected by Zn supple-

mentation (p = 0.51 and p = 0.88 respectively). In all aspects, Se-yeast

was found to be a highly bioavailable form of Se in comparison to sele-

nite. Because of its superior bioavailability, organically bound Se would

be a preferred Se source for supplementation of fishmeal trout diets than

selenite.

DOI: 10.1111/j.1439-0396.2008.00888.x

Journal of Animal Physiology and Animal Nutrition 94 (2010) 99–110 ª 2009 The Authors. Journal compilation ª 2009 Blackwell Verlag GmbH 99

been determined in experiments with semi-purified

diets containing inorganic minerals. Fishmeal-based

diets often contain levels of Se and Zn well above

the requirements, but the availability of both ele-

ments from such diets is lower than that from semi-

purified diets (Bell and Cowey, 1989; Lorentzen and

Maage, 1999). In addition, mineral requirements can

increase during periods of stress, such as may occur

with Se (Halver et al., 2004). Consequently, under

intensive aquaculture conditions, trace element sup-

plementation, particularly Zn, is often necessary to

ensure requirements are met in all conditions.

Because of the higher mineral levels in practical

diets, European Union maximum permitted dietary

levels of Se (0.5 mg/kg) and Zn (250 mg/kg) may

not leave much scope for supplementation. It is

therefore essential that any supplemented minerals

are highly bioavailable; especially Zn and Se. Cur-

rently, any supplementation of commercial and

experimental fish diets is largely from inorganic

sources, namely zinc sulphate (ZnSO4), zinc oxide

(ZnO), and sodium selenite (Na2SeO3).

Organically chelated minerals are becoming

increasingly favoured trace element supplements

over inorganic sources because of their increased

bioavailability. Organic Zn sources are those in

which the Zn ion is chelated by organic tri- or di-

peptides (Zn-proteinates) or single amino acids

(Ashmead, 1992). Organic Se is covalently bound in

selenoproteins by the substitution of sulphur in the

amino acids cysteine and methionine forming ‘sele-

no’ analogs selenocysteine (Se-Cys) and selenome-

thionine (Se-Met) (Allan et al., 1999). These

organically bound minerals, as opposed to inorganic

mineral salts, are referred to as ‘organic’ here

onwards. Natural feed ingredients largely contain

minerals bound to proteins and amino acids; conse-

quently the use of organic minerals is regarded as a

more natural method of trace element supplementa-

tion (Tucker and Taylor-Pickard, 2005). Organic Zn

sources, such as zinc methionine (Zn-Met) and other

Zn amino acid chelates (Zn-AA), have been reported

to be more bioavailable than inorganic Zn in both

mammals and fish (Wedekind et al., 1992; Ashmead,

1992). Zn-Met is more effective in preventing defi-

ciency symptoms (Paripatananont and Lovell, 1995a)

and maintaining host defence against Edwardsiella

ictaluri (Paripatananont and Lovell, 1995b). How-

ever, Li and Robinson (1996) found no difference in

bioavailability between Zn-gluconate and ZnSO4,

and Zn-proteinate was not as bioavailable as antici-

pated in catfish fed practical diets. Organic Se has

shown to be more bioavailable in fish as well as

mammals. In Atlantic salmon (Salmo salar), Se-Met

is more digestible (Bell and Cowey, 1989) and more

efficiently deposited in muscular tissue than selenite

(Lorentzen et al., 1994). Organic Se is also more bio-

available to channel catfish (Ictalurus punctatus)

resulting in increased muscle Se deposition (Wang

and Lovell, 1997) and resistance to Edwardsiella

ictaluri infection (Wang et al., 1997).

The chelation of trace elements by organic com-

pounds may protect metal ions against anti-nutri-

tional factors present in practical diets. The dietary

ingredients of commercial catfish and salmonid

diets contain calcium, phosphorous, and phytic

acid, which can form insoluble and indigestible Zn

compounds in the gut (Gatlin and Wilson, 1984;

Hardy and Shearer, 1985; Richardson et al., 1985;

Satoh et al., 1987a, 1989; Storebakken et al.,

2000). Chelated Zn sources are increasingly

thought to be more bioavailable than inorganic Zn

sources because of the protection of the Zn ion

from the formation of insoluble complexes in the

digestive tract, thus facilitating absorption from the

intestinal lumen (Ashmead, 1992). This has been

reported with Zn-AA sources in trout (Apines

et al., 2001) and Zn-proteinates in catfish (Paripa-

tananont and Lovell, 1997). The degree of chela-

tion between Zn-proteinates differs amongst

manufacturers, yet despite this relatively few stud-

ies exist on the bioavailability of Zn-proteinates in

salmonid fish. Fishmeal diets often contain elevated

levels of Se resulting from the high levels present

in fishmeal; 2 mg/kg in brown low temperature

(LT) fishmeal (unpublished results), and between

1.36 and 2.15 mg/kg in various other fishmeals

(National Research Council, 1993). However, it has

been reported by Bell and Cowey (1989) that Se

in fishmeal is poorly digestible compared to Se-Cys,

Se-Met or selenite supplemented in purified diets.

The poor bioavailability of Se from fishmeal, in

comparison to Se from plant-based ingredients, has

also been reported in chicks fed fishmeal (Cantor

et al., 1975; Gabrielsen and Opstvedt, 1980). Unlike

Zn, Se is not cationic and consequently should not

bind to ligands present in practical diets. Se avail-

ability from fishmeal is thought to be dependent

on the digestibility of the Se compounds within

the diet and their subsequent metabolism (Wang

and Lovell, 1997).

The aim of this study was to determine the bio-

availability of Se-yeast, containing pre-dominantly

selenomethionine, and Zn proteinate (Zn-pr) in a

white fishmeal-based diet in comparison to inorganic

sodium selenite and Zn sulphate in rainbow trout.

Bioavailability of organic and inorganic zinc and selenium sources S. A. Rider et al.

100 Journal of Animal Physiology and Animal Nutrition. ª 2009 The Authors. Journal compilation ª 2009 Blackwell Verlag GmbH

Apparent mineral digestibility was used as a measure

of net mineral uptake from the gut. Tissue and

whole body levels, which are mandatory as a mea-

sure of element uptake in trace element studies (Co-

wey, 1992), were used to show the uptake of Se and

Zn once digested. The specific activities of selected

enzymes dependent on Se and Zn were determined

as a measure of the uptake of these elements into

metabolically active proteins. The enzymes glutathi-

one peroxidase (GSH-Px) and thioredoxin reductase

(TR) were used to assess Se status; the latter being

previously unreported in fish with respect to Se sta-

tus. Zn uptake was measured by the enzymes activi-

ties of carboxypeptidase B (CPB) and alkaline

phosphatase (ALP).

Methods

Experimental design and diets

A 10-week feeding trial was initiated with three die-

tary treatments based on a common basal fishmeal

diet (Table 1); a control (un-supplemented) diet con-

taining only residual Zn and Se; a diet containing

supplemental organic Se and Zn, and a diet contain-

ing supplemental inorganic Se and Zn. Inorganic Zn

and Se were supplemented using ZnSO4 and

Na2SeO3 respectively and organic Se and Zn were

supplemented using Selplex� (Se-yeast) and Bioplex

Zn� (Zn-proteinate) (Alltech Inc., Lexington, KY,

USA) respectively. For the determination of trace

element digestibility, the inert marker yttrium oxide

was added to all diets to provide 1g/kg yttrium oxide

as recommended by Ward et al. (2005).

Rainbow trout (mean weight 31.9 ± 2.1 g) were

acquired from Hatchlands Fisheries, Rattery, Devon,

acclimated to a 20 tank recirculation facility for a

period of 3 weeks and fed ad libitum using a standard

commercial trout diet (15–45 Grower Feed XS, Aller

Aqua, Christianfield, Denmark). Post-acclimation,

fish were stocked into one of nine 125 l tanks at a

density of 25 fish per tank, and each tank was ran-

domly assigned to receive a dietary treatment; each

consisting of three replicate tanks (n = 3). Dissolved

oxygen, temperature and pH were monitored daily

and maintained at (± SEM) 87.6 ± 1.6%, 15.3 ±

0.1 �C and 7.2 ± 0.1 respectively. Total mortality

during the trial was <1%.

All fish in each tank were weighed at t = 0 and

fed 2.2% body weight per day. Throughout the

trial, fish were re-weighed every 2 weeks and feed

input adjusted based on a predicted feed conversion

ratio (FCR) of 1. Feed input was adjusted in the

event of any mortalities. Specific growth rate (SGR)

and FCR were determined using the following

equations;

SGRð%Þ ¼ Ln final wtðgÞ � Ln initial wtðgÞDays fed

� �� 100

FCR ¼ feed inputð g Þ=live weight gainðgÞ

Sample collection

All sampled fish were ethically anaesthetised with

tricane methanesulfonate (MS-222) and euthanized

by severing the anterior most portion of the spinal

cord. Fish were sampled for all analysis at the end of

the 10-week trial period and 1 days feed withdrawal.

Three random fish per tank (nine per treatment)

were dissected for the liver, pyloric caeca and

remaining intestinal tissue for enzyme analysis. The

pyloric caeca was processed whole (fat deposits

removed); the remaining intestinal tissue was sam-

pled, any digesta removed and cleaned with 0.7%

NaCl, and the liver sampled whole. All sampled tis-

sues were stored at )80 �C until analysis. A further

three fish per tank (nine per treatment) were sam-

pled for trace element analysis and the following tis-

sues sampled: liver (whole); kidney (whole); all gills

(gill arches removed); pyloric caeca (whole); mid

and hind intestinal tissue (digesta removed and

cleaned with 0.7% NaCl); spleen (whole); muscle

and corresponding integument (2 · 2 cm3 sections

beneath both sides of the dorsal fin); and the caudal

fin (whole). The remaining carcass was heated at

100 �C for 20 min in order that the whole vertebrae

could be removed and sampled from surrounding

soft tissues. All tissues were freeze-dried and

Table 1 Basal diet formulation

Ingredient % of diet

White fishmeal* 64

Marine fish oil� 15

Wheat middlings (4-05-205) 19.82

Vitamin premix� 0.5

Se/Zn variable premix§ 0.5

Se/Zn free premix– 0.18

*Provimi 66 white fishmeal, Provimi Ltd, UK.

�Seven Seas Ltd, Hull, UK.

�Skretting, Preston, UK.

§5% variable Se and Zn premix with yttrium oxide to provide 1 mg/kg

Y2O3. Inorganic Se (Na2SeO3) and Zn (ZnSO4Æ7H2O) Sigma, UK. Organic

Se yeast (Selplex�) and Zn-Proteinate (Bioplex Zn�), Alltech inc., KY,

USA.

–Se and Zn free premix [supplementing the following in mg/kg; Fe 34

(FeSO4.7H2O), Cu 5 (CuSO4.5H2O), I 6 (KI), Mn 15 (MnSO4ÆH2O)].

S. A. Rider et al. Bioavailability of organic and inorganic zinc and selenium sources

Journal of Animal Physiology and Animal Nutrition. ª 2009 The Authors. Journal compilation ª 2009 Blackwell Verlag GmbH 101

percentage moisture determined from initial and

final weights. Dried tissues were pooled per treat-

ment and homogenised. For the analysis of whole

body Se and Zn an additional four fish per tank (12

per treatment) were sampled, dried whole at 105 �Cuntil a constant weight and moisture content deter-

mined prior homogenisation for whole body trace

element analysis.

Determination of apparent digestibility

For the analysis of apparent digestibility, fish were

anaesthetised and faecal material was stripped by

hand from all fish by applying pressure on the hind

portion of the peritoneal cavity on week 8. Faecal

material was pooled for each replicate tank, and

dried at 105 �C for 24 h prior to Se, Zn and yttrium

(Y), analysis. Apparent digestibility was determined

using the following equation (Paripatananont and

Lovell, 1997):

Apparent digestibility

¼ 100� 1� ½Ydiet� � ½Elementfaeces�½Yfaeces� � ½Elementdiet�

� �

Proximate analysis of diets

Energy, protein, lipid, ash and moisture were deter-

mined according methods of the AOAC (2007)

(Table 2).

Trace metal analysis of diets, whole body and fish

tissues

All samples were digested in at least triplicate in

concentrated nitric acid at 120 �C using a micro

Kjeldhal digestion block. Dietary and faecal Y was

analysed by inductively coupled plasma (ICP) optical

emission spectrometry. Zn analysis was carried out

by flame atomic absorption spectrometry and Se was

determined (LGC, Teddington, UK) by ICP mass

spectrometry with standard additions. Dorm-2 (dog-

fish muscle) (National Research Council, Canada)

was used as a reference standard in all analysis con-

firming 100% recovery for both elements, ±10% for

Se and 5% for Zn.

Determination of zinc and selenium-dependent

enzymes

All enzyme activities were normalised to sample pro-

tein concentration with the spectrophotometric bi-

cinchonic acid method (Smith et al., 1985).

Glutathione peroxidase was measured according to

Bell et al. (1986) with modifications. Briefly, liver

samples (n = 9) were homogenised 1 in 9 volumes

100 mm Tris-HCl buffer (pH 7.4) with, 2.5 mm

EDTA, 0.01% Triton-X100 and 2.5 mm sodium

azide. A 50 ll homogenate was added to an assay

mixture containing 0.96 mm reduced glutathione,

0.96 units/ml glutathione reductase and 0.19 mm

NADPH. The rate of non-GSH-Px oxidation of

NADPH was determined and subtracted from the

rate of oxidation of NADPH after the addition of

1.23 mm cumene hydroperoxide at 340 nm. GSH-Px

activity was calculated as nmol NADPH oxidised

min/mg protein.

Thioredoxin reductase was measured by modifica-

tion of the method described by Hill et al. (1997).

Tissues (n = 9) were homogenised and dialysed 1 in

9 volumes 0.01 m phosphate buffer saline pH 7.4

(PBS) (2.7 mm KCl, 0.137 m NaCl,) containing 2 mm

EDTA. Dialysis was performed to remove endoge-

nous GSH using 12–14000 Daltons Visking tubing.

The assay mixture contained 0.176 U oxidised thior-

edoxin, 0.38 mg insulin and 0.12 mg NADPH in

160 ll of 1 m 4-(2-hydroxyethyl)piperazine-1-etha-

nesulfonic acid (HEPES) with 10 mm EDTA. The

reaction was started by adding 30 ll sample and

incubated for 30 min at 25 �C. 750 ll of 0.4 mg/ml

DTNB in 6 m guanidine hydrochloride was added to

stop the insulin reaction and absorbance read at

412 nm. Reciprocal assays were run without

Table 2 Composition of experimental diets and growth performance*

Diet

Basal

Organic

Se & Zn

Inorganic

Se & Zn

Mean SEM Mean SEM Mean SEM

Moisture� 4.0 0.2 4.2 0.2 4.6 0.3

Protein� 43.6 0.2 42.9 0.4 42.9 0.1

Lipid� 19.8 0.5 21.3 0.2 20.1 0.2

Ash� 11.9 0.5 12.3 0.1 11.9 0.3

Energy� 20.55 0.01 20.94 0.00 20.74 0.05

Iron§ 181.9 0.0 178.4 3.3 173. 3 0.1

Copper§ 41.1 0.1 42.1 0.8 44. 2 1.2

Manganese§ 75.6 1.0 73.0 2.0 75.7 4.0

Zinc§ 157.3 3.1 306.7 3.1 246.3 1.6

Selenium§ 1.16 0.01 1.86 0.01 1.79 0.01

SGR– 2.07a 0.03 1.87a 0.08 1.95a 0.07

FCR– 1.06a 0.02 1.15a 0.05 1.12a 0.04

*Proximate analysis of experimental diets on as fed wet weight basis.

�Value in %.

�Value in MJ/kg.

§Value in Mg/kg.

–Means in the same row not sharing a common superscript are signifi-

cantly different (p £ 0.05).



thioredoxin to determine the activity of non-TR-

dependant reduction, which was subtracted from the

TR-dependant reaction and TR activity is given in

A412 units · 1000/min/mg protein (Holmgren and

Bjornstedt, 1995).

Alkaline Phosphatase was determined on intestinal

tissue homogenates (n = 9) using a method based on

Walter and Schutt (1974). Tissues were homogen-

ised 1 in 9 volumes PBS buffer. 50 ll of homogenate

was added to 2 ml 97.5 mm diethanolamine sub-

strate solution (pH 9.8) with 0.5 mm MgCl and

1.21 mm 2-amino-2 methyl propanol (pnpp) and

incubated at 25 �C for 30 min. The reaction was ter-

minated with 10 ml 0.05 m NaOH and absorbance

read at 405 nm. Background activity of a blank was

subtracted and units mg/protein determined as by

Walter and Schutt (1974).

Carboxypeptidase B was measured in the pyloric

caeca according to the method of Ramseyer et al.

(1999). Whole pyloric caeca samples (n = 9) were

homogenised 1 in 9 volumes PBS buffer. A 25 ll

sample was added to 2.975 ml assay cocktail con-

taining 25 mm Tris-HCl (pH 7.65) with 100 mm NaCl

and 1.0 mm Hippuryl-l-Arginine. Reaction rate at

25 �C was followed over 5 min at 254 nm. Units

CPB were calculated using a molar extinction coeffi-

cient of hippuric acid of 0.36 (Folk et al., 1960) and

normalised to mg sample protein.

Statistical analysis

All means are reported with standard error of the

mean (SEM). Statistical analysis was performed on

spss version 15. Data was tested for homogeneity

of variance (Levene and Kolmogorov–Smirnov

tests), and modelled by one-way anova. Percentage

digestibility data was arcsine transformed prior to

statistical analysis. Any significant differences

among treatment means given by the anova model

were evaluated by a post hoc Tukey honestly signif-

icant difference (HSD) test. Significance was set at

p < 0.05 for all statistical tests.

Results

Growth rates and feed performance

Growth rates and feed conversion ratios were within

expected ranges for trout under production condi-

tions (Table 2). After 10 weeks, fish almost quadru-

pled in weight to a mean of 125.3 ± 19.2g.

Throughout the 10-week period, there was no signif-

icant difference between treatments for SGR

(p = 0.163) and FCR (p = 0.3).

Selenium and zinc digestibility

Se-yeast digestibility was significantly higher than

both the control and selenite diets, and Zn digestibil-

ity was similar across all treatments. Mean (±SEM)

apparent digestibility (Fig. 1) of residual Zn and Se

in the basal diet was 22 ± 1% and 54 ± 2% respec-

tively. Apparent Zn digestibility (Fig. 1) was highest

for the basal diet group followed by the Zn-pr and

ZnSO4 groups; the latter having the lowest digestibil-

ity. However, trends in Zn digestibility were not sig-

nificant (p = 0.089). The apparent digestibility of Se

(Fig. 1) was significantly higher for the Se-yeast-

supplemented group than either the control or sele-

nite-supplemented fish, which did not differ from

each other (p = 0.34).

Whole body zinc and selenium levels

Whole body Se and Zn were both affected by sup-

plementation and levels were dependent on min-

eral source. Significant differences in whole body

Zn were observed between treatments. Both Zn

sources increased whole body Zn with ZnSO4

supplementation resulting in a greater increase

than Zn-pr (Table 3). Se-yeast supplementation

significantly increased whole-body Se and sele-

nite supplementation had no effect (p = 0.54)

(Table 4).

Tissue zinc

In those tissues which responded to supplemented

Zn, increases were greater for ZnSO4; the only

0

10

20

30

40

50

60

70

Se Zn

Per

cen

tag

e ap

par

ent

dig

esti

blil

ity

Control basal diet

Added organic Zn & Se

Added inorganic Zn & Sea

b

a

aa a

Fig. 1 Mean (±SEM) apparent digestibility (%) of zinc and selenium.

Different lower case letters indicate significant difference for each ele-

ment (p £ 0.05).



exception being the liver (Table 3). Despite the

higher Zn level in Zn-pr than the ZnSO4 diet, Zn in

the muscle, vertebrae and plasma was only signifi-

cantly increased by ZnSO4. A similar trend was

found in the gill tissue, where both sources of sup-

plemented Zn resulted in increased levels of the ele-

ment, but by a significantly greater extent from

ZnSO4 than from Zn-pr. Neither ZnSO4 nor Zn-pr

significantly increased Zn in the whole blood, integ-

ument or caudal fin (p = 0.283, 0.147 and 0.338

respectively). ZnSO4 supplementation did not signifi-

cantly increase kidney Zn above that of the basal

diet (p = 0.186), and Zn-pr resulted in a significantly

reduced kidney Zn. Only Zn-pr resulted in a signifi-

cant increase in liver Zn above the basal diet. The

higher Zn levels in the Zn-pr diet were not reflected

in the pyloric caeca; only ZnSO4 significantly

increased Zn in this tissue. A similar trend was found

in the posterior intestinal tissue, where both sources

increased Zn but ZnSO4 resulting in a significantly

greater increase.

Tissue selenium

Tissue Se levels indicated that organic Se-yeast is dis-

tributed differently to selenite (Table 4). There was a

Table 3 Mean tissue and whole-body Zn with

standard error of mean (SEM) of trout fed

diets with different Zn sources*Diet�

Basal Zn–prot ZnSO4


Whole Body (n = 6) 28.8a 0.5 31.2b 0.4 32.7c 0.2

Gill 105.0a 0.7 121.2b 0.9 128.6c 1.4

Plasma 10.6a 0.2 11.8a 0.6 13.7b 0.5

Vertebrae (n = 3) 85.8a 5.3 80.1a 2.1 159.6b 8.3

Integument (n = 3) 42.2a 1.8 46.9a 1.9 47.3a 1.4

Whole Blood 11.0a 0.5 11.0a 0.3 11.9a 0.4

Muscle (n = 4) 4.87a 0.02 5.08ab 0.05 5.19b 0.10

Caudal Fin (n = 3) 48.2a 2.0 50.8a 1.0 53.7a 4.2

Liver 17.1a 0.2 19.0b 0.3 18.4a 0.6

Kidney 21.5a 0.3 20.0b 0.3 22.0a 0.3

Pyloric Caeca (including digesta) (n = 3) 186.1a 1.0 216.6a 8.7 257.9b 8.3

Posterior intestinal tissue

(excluding digesta) (n = 2)

307a 12.9 392.2b 14.0 404.8bc 3.4

*Mean values in mg/kg (wet weight). Means in the same row not sharing a common superscript

are significantly different (p £ 0.05). All tissues (n = 5) unless stated.

�For details see Table 1.

Table 4 Mean tissue and whole-body Se with

standard error of mean (SEM) of trout fed

diets with different Se sources*Diet�

Basal Se-yeast Selenite


Whole Body 0.24a 0.01 0.36b 0.01 0.26a 0.01

Muscle 0.21a 0.01 0.37b 0.01 0.23a 0.01

Integument 0.40a 0.00 0.61b 0.01 0.46c 0.00

Gill 0.40a 0.00 0. 51b 0.00 0.43c 0.00

Whole Blood 0.45a 0.00 0.58b 0.01 0.52c 0.00

Plasma 0.14a 0.00 0.19b 0.00 0.17c 0.00

Spleen (n = 1)� 0.77 1.01 0.80

Kidney 0.90a 0.02 1.07b 0.02 0.99c 0.01

Liver 2.04a 0.04 3.65b 0.07 3.75b 0.05

Pyloric Caeca (including digesta) 0.73a 0.01 0.92b 0.01 1.17c 0.01

Posterior intestinal tissue

(excluding digesta) (n = 2)

0.36a 0.00 0.38ab 0.01 0.34ac 0.00

*Mean values in mg/kg (wet weight). Means in the same row not sharing a common superscript

are significantly different (p £ 0.05). All tissues (n = 3) unless stated.

�For details see Table 1.

�Statistical comparison could not be made because of lack of replication.



significantly lower Se content in the pyloric caeca of

the Se-yeast than selenite-supplemented group. In

all remaining tissues except the liver, the Se-yeast

group had a significantly higher Se level than the

basal and selenite groups. Both Se-yeast and selenite

supplementation significantly increased Se in the

kidney, plasma, integument and whole blood, but

increased Se was significantly lower for selenite than

Se-yeast supplementation. Liver Se was significantly

elevated to a similar extent in both supplemented

groups. Selenite did not increase muscular Se signifi-

cantly (p = 0.85).

Selenium- and zinc-dependent enzyme activity

In all measured enzymes, only selenium-dependent

TR activity in the organic Se supplemented fish

responded to supplemented Se. Activities of both

intestinal ALP (p = 0.51) and pyloric caeca CPB

(p = 0.89) were not affected by either forms of Zn

supplementation (Table 5). This is also reflected in

the Zn enzyme activity/tissue Zn ratios, which were

not significantly different for intestinal ALP

(p = 0.64) or CPB (p = 0.22). There was no signifi-

cant effect by either source of supplemented Se on

GSH-Px activity (p = 0.059) or GSH-Px/tissue Se

ratios (p = 0.065) (Table 6). TR activity significantly

increased as a result of Se-yeast supplementation,

but was not affected by selenite. The TR activity/tis-

sue Se ratio was greater for Se-yeast than selenite,

but not significantly (p = 0.056).

Discussion

This study was undertaken to determine the bio-

availability of organic and inorganic Se and Zn

sources in white fishmeal-based trout diets. The

nutritional value of a trace element depends both on

dietary levels and bioavailability, which can be

affected by both physiological and dietary factors.

Dietary factors which influence trace element bio-

availability in practical diets include the chemical

forms of elements in the diet, the formation of insol-

uble complexes by interactions with dietary compo-

nents, and antagonistic effects of other elements

(O’Dell, 1984). To take into account the potential of

such dietary anti-nutritional factors, the basal diet of

this study was formulated with white fishmeal and

wheat middlings to contain relatively high levels of

potential Zn inhibitors and a decreased Se content.

As mineral supplementation in fishmeal diets may

often require both Se and Zn, they were co-supple-

mented and the bioavailability of both evaluated

using markers specific to each element. Previously

House and Welch (1989) showed that in rats high

levels of either Zn or Se can have antagonistic effects

on one another. As both Se and Zn were above

requirements, any such interactions are not expected

to be significant. In Atlantic salmon (Salmo salar)

dietary Se has no significant effect on hepatic Zn

between 0.66 and 2.6 mg Se/kg (Julshamn et al.,

1990). Although comparisons have been made

among other Zn-proteinates, products from different

manufacturers may be produced as such that they

have different degrees of Zn chelation, which may

affect their metabolism and bioavailability (Cao

et al., 2000).

No difference in Zn digestibility was found

between supplemented sources and digestibility of

residual Zn in the basal diet was low. White fish-

meal, with larger concentrations of calcium and

phosphorous in comparison to higher quality fish

Table 5 Zn-dependent enzyme activity and Zn enzyme activity/tissue

Zn ratios with standard error of mean (SEM) of trout fed diets with dif-

ferent Zn sources*

Diet Enzyme

Basal Zn-prot ZnSO4


Intestinal ALP� 0.14a 0.02 0.16a 0.04 0.18a 0.03

P.C. CPB� 1.12a 0.11 1.06a 0.12 1.05a 0.10

Intestinal ALP/Zn ratio� � 0.41a 0.06 0.44a 0.04

P.C. CPB/Zn ratio� � 4.90a 0.49 4.07a 0.44

*Mean values (n = 9). Means in the same row not sharing a common

superscript are significantly different (p £ 0.05). Tissue Zn determined

on a wet weight basis.

�Units mg/protein.

�Tissue Zn in g/kg.

Table 6 Se-dependent enzyme activity and Se enzyme activity/tissue

Se ratios with standard error of mean (SEM) of trout fed diets with dif-

ferent Se sources*

Diet Enzyme

Basal Se-yeast Selenite


Hepatic TR� 0.77a 0.09 1.15b 0.15 0.83ab 0.09

Hepatic GPX� 68.3a 3.4 79.0a 1.6 77.8a 4.3

Hepatic TR /Se ratio� § 0.32a 0.04 0.22a 0.02

Hepatic GPX/Se ratio� § 21.6a 0.4 20.7a 1.2

*Mean values (n = 9). Means in the same row not sharing a common

superscript are significantly different (p £ 0.05). Tissue Se determined

on a wet weight basis.

�A412.1000 min/mg protein.

�nmol NADPH oxidised/min/mg protein.

§Tissue Se in mg/kg.



meals (National Research Council, 1993), and phytic

acid from plant material, can significantly reduce Zn

digestibility because of the formation of insoluble

complexes with the Zn cation (Richardson et al.,

1985; McClain and Gatlin, 1988; Satoh et al., 1993,

1987a,b; Ramseyer et al., 1999; Storebakken et al.,

2000). Consequently, white fishmeal diets can

require Zn supplementation (Satoh et al., 1987b).

Previous studies, which have used significantly lower

levels of dietary Zn than this study, have reported a

significantly higher digestibility of chelated Zn

sources than ZnSO4 (Paripatananont and Lovell,

1997; Apines et al., 2001). The lack of significant dif-

ference between the digestibilities of supplemented

Zn sources in this study may have been affected by

‘diminished returns’ as Zn retention decreases with

increasing Zn (Spry et al., 1988). Both Zn sources

accumulated in the pyloric caeca and posterior intes-

tine, but the highest levels were found in the ZnSO4

group, despite a higher dietary Zn in the Zn-pr diet.

The decreased Zn in the pyloric caeca and intestine

of Zn-pr supplemented trout may either be because

of a decreased accumulation or increased uptake of

Zn-pr than ZnSO4; the latter being favoured because

of the trends in digestibility. An increased sediment

Zn accumulation of 87% under salmon farm cages is

a consequence of dietary Zn excretion; therefore any

increased Zn digestibility would alleviate this heavy

metal pollution (Dean et al., 2007).

Zn in the whole body and majority of tissues

increased to a greater extent by ZnSO4 than Zn-pr

indicating a higher retention for inorganic Zn in

diets above Zn requirements. In salmonids, whole

body Zn correlates well with Zn status (Wekell et al.,

1986). Despite the higher Zn in the Zn-pr group,

ZnSO4, supplemented trout had a marginally greater

whole body Zn indicating a slightly higher retention

of ZnSO4. Increases in whole body Zn by Zn supple-

mentation were much lower than that found in pre-

vious salmonid studies using lower levels of dietary

Zn (Apines et al., 2001; Maage et al., 2001), and is

likely to be a result of the tight regulation of Zn at

levels above requirements (Clearwater et al., 2002).

Gatlin and Wilson (1984) reported a plateau in bone

zinc concentration in catfish above 150 mg/kg using

Zn oxide. This is consistent with the increased Zn in

the gills (particularly the ZnSO4 group) of supple-

mented fish. The gills play a major role in Zn regula-

tion through the excretion of excess Zn (Hardy

et al., 1987 and Maage and Julshamn, 1993). Zn-pr

has been found to effectively raise whole body Zn,

but its increased bioavailability decreases markedly

in diets containing high levels of calcium phosphate

such as those used in this study (Hardy and Shearer,

1985). ZnSO4 supplementation significantly elevated

Zn in the plasma, vertebrae, and muscle, but this

was not found for Zn-pr, again showing a higher

retention of ZnSO4. A slight increase in liver Zn was

found in the Zn-pr supplemented fish but may

merely reflect the higher Zn in this diet than the

ZnSO4 diet. Because of its metabolic rather than

storage role, Zn turns over rapidly in the liver

(Vallee and Falchuk, 1993), and consequently a

measurement of Zn turnover would be a better mea-

surement of Zn status than Zn levels. The results of

Zn in the vertebrae were similar to those of Do

Carmo e Sa et al. (2005) in Nile tilapia (Oreochromis

niloticus) fed practical diets, who found reduced bone

deposition of Zn from Zn-AA than ZnSO4. The differ-

ent response in tissue Zn between organic and inor-

ganic Zn sources suggests a different metabolism

between organic and inorganic Zn post absorption.

Zn supplementation did not affect the activity of

Zn-dependent enzymes, which confirms that Zn

requirements were met by the basal diet. The activ-

ity of both CPB and ALP are dependent on the pres-

ence of Zn at their active site (Coleman, 1992; Folk

et al., 1960). Using 61% plant-based diets in rain-

bow trout, Ramseyer et al. (1999) reported that both

CPB and ALP increased between dietary Zn levels of

51.1 and 133 mg/kg. In this study, basal Zn levels

were higher (157 mg/kg) and Zn enzyme activities

remained the same across all treatments. Using a cod

muscle- and corn meal-based diet, plasma ALP pla-

teaus between 40 and 80 mg/kg in Atlantic salmon

(Maage and Julshamn, 1993), which also supports

the notion that the basal diet met Zn requirements.

Below 100 mg/kg dietary Zn, Zn-AA increases

plasma ALP activity to a greater extent than ZnSO4

supplemented diets (Apines et al., 2001, 2003;

Apines-Amar et al., 2004).

Digestibility of endogenous Se was relatively low,

and was only raised through Se-yeast supplementa-

tion. The digestibility of residual Se from the basal

diet was similar to that found in Atlantic salmon fed

a fishmeal-based diet (46%) (Bell and Cowey,

1989). European Union maximum permitted limits

of dietary Se (0.5 mg/kg) may come very close to,

or because of bioavailability fall short of, the

0.35 mg/kg requirement, particularly during periods

of stress where Se utilisation may increase (Felton

et al., 1989). In this study, Se-yeast significantly

increased Se digestibility, but selenite did not raise

Se digestibility above that of the basal diet. Both

Se sources accumulated in the pyloric caeca,

with the highest levels resulting from selenite



supplementation, which is proposed to correspond

to its reduced absorption. Conversely, the lower

pyloric caeca Se level of the Se-yeast group is

expected to be attributable to increased Se uptake,

which corresponds with the increased plasma Se

and digestibility. Unlike Zn, Se is not cationic and is

not expected to be involved in the dietary effects

that reduce Zn availability. Se in cod muscle is pre-

dominantly organic; containing at least 50% pro-

tein-bound Se-Met (Huerta et al., 2004) and 12%

selenite (Crews et al., 1996). Bell and Cowey (1989)

reported that in Atlantic salmon Se-Met has a

91.6% digestibility in a semi-purified diet. Despite

supplementing an additional 62% Se-yeast, which

contains pre-dominantly Se-Met, only a 15.6%

improvement in digestibility was achieved. This sug-

gests that Se absorption from fishmeal, especially for

selenite, are affected by dietary factors that are yet

to be identified. Mineral interactions such as the

antagonistic effects of copper may be one of the

contributing factors in reduced Se digestibility from

fishmeals, as described by Lorentzen et al. (1998).

Tissue and whole body Se analysis demonstrated

that Se-yeast is more bioavailable than selenite and

both sources are metabolised differently. Whole body

Se is a good measure of Se status (Hilton et al.,

1980; Lin and Shiau, 2005) and was significantly

greater for Se-yeast than selenite supplementation.

This has also been reported in Atlantic salmon

(Lorentzen et al., 1994) and catfish (Wang and

Lovell, 1997). The greatest Se accumulations in

plasma, integument, whole blood and kidney

resulted from Se-yeast supplementation. Although

not significant, the exception to this was hepatic Se,

which was increased to the greatest extent by sele-

nite. The elevation of Se from selenite in the liver,

but not the muscle and whole body, suggest inor-

ganic Se is metabolised differently, as reported by

Bell and Cowey (1989). Selenite will follow the reg-

ular pathway for metabolism of Se but Se-yeast with

a high Se-Met content will also follow pathways for

methionine (Burk, 1976). Se-yeast supplementation

of trout resulted in elevated Se in all tissues and is

principally attributable to the non-specific incorpora-

tion of Se-Met into proteins of the soft tissues

(Schrauzer, 2000). Likewise, Lorentzen et al. (1994)

showed that the non-specific incorporation of sele-

nite does not occur to any significant extent in

salmon and this is verified in this study for trout.

The Se enrichment of fillets by Se-yeast may be of

potential benefit to European consumers, which are

generally thought to be Se-deficient (Rayman, 2000;

Cotter et al., 2008).

TR activity was only increased by Se-yeast supple-

mentation, and as dietary Se was above require-

ments, activity of GSH-Px was not affected. Both

GSH-Px and TR are dependent on Se for their activ-

ity (Allan et al., 1999). As GSH-Px responds well to

Se status, it is routinely used to study Se status in

piscine as well as mammalian studies. However, this

Se-dependent enzyme only responds to dietary Se at

marginal levels (Bell et al., 1986, 1987). At higher

dietary Se, a plateau in GSH-Px activity occurs,

which is commonly used to determine dietary Se

requirements; Hilton et al. (1980) based their Se

requirement for rainbow trout on a maximal plasma

GSH-Px activity at 0.35 mg/kg dietary Se. Both this

study and previous studies, using dietary Se above

requirements, report no effect on hepatic or plasma

GSH-Px (Bell and Cowey, 1989). In this study and

in hybrid striped bass ( Morone chrysops x M. saxatilis),

GSH-Px activity is not affected by dietary Se source

(Cotter et al., 2008). The Se requirement for other

Se enzymes may differ from that of GSH-Px; conse-

quently TR was included in this study. Its activity

has been found to respond to dietary Se in mammals

(Hill et al., 1997), even to supranutritional levels in

rats (Berggren et al., 1999). The determination of its

activity was particularly relevant to this study, as

dietary Se was expected to be close to GSH-Px

requirements. The increase in TR activity by Se-yeast

in this study shows that the requirements of Se

enzymes differ and that Se source is an important

factor for its activity. It is recognised that fishes con-

tain at least 18 genes for Se-containing proteins

including selenoprotein P, which contains 10 Se resi-

dues in mammals but 17 in fish, which may indicate

a higher Se utilisation in fish (Kryukov and

Gladyshev, 2000).

Conclusion

In summary, this study has shown that the bioavail-

ability of organic and inorganic Se and Zn sources

differ in white fishmeal diets. Zn digestibility and

Zn-dependent enzymes were not affected by either

forms of supplemented Zn, which is expected as Zn

levels in the basal diet were above requirements.

ZnSO4 accumulated to a greater extent than Zn-pr

in tissues showing a higher retention when Zn is

above requirements. In all factors assessed, Se bio-

availability was greater for organic Se-yeast than sel-

enite. Organic Se yeast proved to be highly

efficacious, increasing digestibility of overall dietary

Se, efficiently raising whole body and tissue Se sta-

tus, as well as increasing TR activity. This was not



the case with selenite, which in this study did not

prove to be as highly bioavailable. Because of the

differences in their metabolism, particularly in fish-

meal-based diets, and potential as efficient supple-

ments, requirements for organic minerals in practical

diets should be determined, especially for Se.

Acknowledgements

The authors would like to express their gratitude to

Dr A. Fisher, Dr T. Henry and L. Folland for their

technical assistance. This study was made possible

by funding from a BBSRC and Alltech Inc. CASE

studentship.

References

Allan, C. B.; Lacourciere, G. M.; Stadtman, T. C., 1999:

Responsiveness of selenoproteins to dietary selenium.

Annual Review of Nutrition 19, 1–16.

AOAC, 2007: Official Methods of Analysis of the Association

of Analytical Chemists. 18th edn. AOAC, Maryland, USA.

Apines, M. J.; Satoh, S.; Kiron, V.; Watanabe, T.; Nasu,

N.; Fujita, S., 2001: Bioavailability of amino acids

chelated and glass embedded zinc to rainbow trout,

Oncorhynchus mykiss, fingerlings. Aquaculture Nutrition 7,

221–228.

Apines, M. J.; Satoh, S.; Kiron, V.; Watanabe, T.; Fujita,

S., 2003: Bioavailability and tissue retention of amino

acid-chelated trace elements in rainbow trout On-

coryhynchus mykiss. Fisheries Science 69, 722–730.

Apines-Amar, M. J. S.; Satoh, S.; Caipang, C. M. A.;

Kiron, V.; Watanabe, T.; Aoki, T., 2004: Amino acid-

chelate: a better source of Zn, Mn and Cu for rain-

bow trout, Oncorhynchus mykiss. Aquaculture 240,

345–358.

Ashmead, H. D., 1992: The Roles of Amino Acid Chelates in

Animal Nutrition. Noyes Publications, New Jersey, USA.

Bell, G. J.; Cowey, C. B., 1989: Digestibility and bioavail-

ability of dietary selenium from fishmeal, selenite, sele-

nomethionine and selenocysteine in Atlantic salmon

(Salmo salar). Aquaculture 81, 61–68.

Bell, J. G.; Pirie, B. J. S.; Ardon, J. W.; Cowey, C. B.,

1986: Some effects of selenium deficiency on glutathi-

one peroxidise (EC 1.11.1.9) activity and tissue pathol-

ogy in rainbow trout (Salmo gairdneri). British Journal of

Nutrition 55, 305–311.

Bell, J. G.; Cowey, C. B.; Adron, J. W.; Pirie, J. S., 1987:

Some effects of selenium deficiency on enzyme activi-

ties and indices of tissue peroxidation in salmon parr

(Salmo salar). Aquaculture 65, 43–54.

Berggren, M. M.; Mangin, J. F.; Gasdaska, J. R.; Powis,

G., 1999: Effect of selenium or rat thioredoxin reduc-

tase activity. Biochemical Pharmacology 57, 187–193.

Burk, R. F., 1976: Selenium in man. In: A. S. Prasad

(ed.), Trace Elements in Human Health and Disease. Aca-

demic Press, London, 105–134.

Cantor, A. H.; Scott, M. L.; Noguchi, T., 1975: Biological

availability of selenium in feedstuffs and selenium

compounds for prevention of exudative diathesis in

chicks. Journal of Nutrition 105, 96–105.

Cao, J.; Henry, P. R.; Guo, R.; Holwerda, R. A.; Toth, J.

P.; Littell, R. C.; Miles, R. D.; Ammerman, C. B., 2000:

Chemical characteristics and relative bioavailability of

supplemental organic zinc sources for poultry and

ruminants. Journal of Animal Science 78, 2039–2054.

Clearwater, S. J.; Farag, A. M.; Mayer, J. S., 2002: Bio-

availability and toxicity of dietborne copper and zinc to

fish. Comparative Biochemistry and Physiology 132C, 269–

313.

Coleman, J. E., 1992: Structure and mechanism of alka-

line phosphatase. Annual Review of Biophysics and Biomo-

lecular Structure 21, 441–483.

Cotter, P. A.; Craig, S. R.; Mclean, E., 2008: Hyperaccu-

mulation of selenium in hybrid striped bass: a func-

tional food for aquaculture? Aquaculture Nutrition 14,

215–222.

Cowey, C. B., 1992: Nutrition: estimating requirements

of rainbow trout. Aquaculture 100, 177–189.

Crews, H. M.; Clarke, P. A.; Lewis, J. D.; Owen, L. M.;

Strutt, P. R., 1996: Investigation of selenium speciation

in in vitro gastrointestinal extracts of cooked cod by

high-performance liquid chromatography-inductively

coupled plasma mass spectrometry and electrospray

mass spectrometry. Journal of Analytical Atomic Spectro-

metry 11, 1177–1182.

Dean, R. J.; Shimmield, T. M.; Black, K. D., 2007: Cop-

per, zinc and cadmium in marine cage fish farm sedi-

ments: an extensive survey. Environmental Pollution

145, 84–95.

Do Carmo e Sa, M. V.; Pezzato, L. E.; Barros, M. M.; De

Magalhaes Padilha, P., 2005: Relative bioavailability of

zinc in supplemental inorganic and organic sources for

Nile tilapia Oreochromis niloticus fingerlings. Aquacul-

ture Nutrition 11, 273–281.

Felton, S. P.; Smith, L. S.; Ji, W.; Halver, J. E., 1989:

Implications of selenium involvement during chemical

and physical stress in salmonids. Proceedings of the Soci-

ety for Experimental Biology and Medicine 190, 303.

Folk, J. E.; Piez, K. A.; Carrol, W. R.; Gladner, J. A.,

1960: Carboxypeptidase B. IV. Purification and charac-

terization of the porcine enzyme. Journal of Biological

Chemistry 235, 2272–2277.

Gabrielsen, B. O.; Opstvedt, J., 1980: Availability of sele-

nium in fishmeal in comparison with soybean meal,

corn gluten meal and selenomethionine relative to

selenium in sodium selenite for restoring glutathione

peroxidise activity in selenium-depleted chicks. Journal

of Nutrition 110, 1096–1100.



Gatlin, D. M.; Wilson, R. P., 1984: Zinc supplementation

of practical channel catfish diets. Aquaculture 41, 31–

36.

Halver, J. E.; Felton, S. M.; Zbanyszek, R., 2004: Carcass

selenium loss as an indicator of stress in barrage trans-

ported Chinook salmon (Oncorhynchus tshawytscha).

Aquaculture Research 35, 1099–1103.

Hardy, R. W.; Shearer, K. D., 1985: Effect of dietary cal-

cium phosphate and zinc supplementation on whole

body zinc concentration of rainbow trout (Salmo gaird-

neri). Canadian Journal of Animal Science 42, 181–184.

Hardy, R. W.; Sullivan, C. V.; Koziol, A. M., 1987:

Absorption, body distribution, and excretion of dietary

zinc by rainbow trout (Salmo gairdneri). Fish Physiology

and Biochemistry 3, 133–143.

Hill, K. E.; McCollum, G. W.; Boeglin, M. E.; Burk, R. F.,

1997: Thioredoxin reductase activity is decreased by

selenium deficiency. Biochemical and Biophysical Research

Communications 234, 293–295.

Hilton, J. W.; Hodson, P. V.; Slinger, S. J., 1980: The

requirement and toxicity of selenium in Rainbow trout

(Salmo gairdneri). Journal of Nutrition 110, 2527–2535.

Holmgren, A.; Bjornstedt, M., 1995: Thioredoxin and thi-

oredoxin reductase. Methods in Enzymology 252, 199–

208.

House, W. A.; Welch, R. M., 1989: Bioavailability of and

interactions between zinc and selenium in rats fed

wheat grain intrinsically labelled with 65Zn and 75Se.

Journal of Nutrition 119, 916–921.

Huerta, V. D.; Sanchez, M. L. F.; Sanz-Medel, A., 2004:

Quantitative selenium speciation in cod muscle by iso-

tope dilution ICP-MS with a reaction cell: comparison

of different reported extraction procedures. Journal of

Analytical Atomic Spectrometry 19, 644–648.

Julshamn, K.; Sandnes, K.; Lie, O.; Waagbo, R., 1990:

Effects of dietary selenium supplementation on growth,

blood chemistry and trace element levels in serum and

liver of adult Atlantic salmon (Salmo salar). Fiskeridirek-

toratets Skrifter Serie Ernaering III 2, 47–58.

Kryukov, G. V.; Gladyshev, V. N., 2000: Selenium metab-

olism in zebrafish: multiplicity of selenoprotein genes

and expression of a protein containing 17 selenocyste-

ine residues. Genes to Cells 5, 1049–1060.

Li, M. H.; Robinson, E. H., 1996: Comparison of chelated

zinc and zinc sulphate as zinc sources for growth and

bone mineralization of channel catfish (Ictalurus puncta-

tus) fed practical diets. Aquaculture 146, 237–243.

Lin, Y.; Shiau, S., 2005: Dietary requirements of juvenile

grouper Epinephelus malabaricus. Aquaculture 250, 356–

363.

Lorentzen, M.; Maage, A., 1999: Trace element status of

juvenile Atlantic salmon Salmo salar L. fed a fish-meal

based diet with or without supplementation of zinc,

iron, manganese and copper from first feeding. Aqua-

culture Nutrition 5, 163–171.

Lorentzen, M.; Maage, A.; Julshamn, K., 1994: Effects of

dietary selenite or selenomethionine on tissue sele-

nium levels of Atlantic salmon (Salmo salar). Aquacul-

ture 121, 359–367.

Lorentzen, M.; Maage, A.; Julshamn, K., 1998: Supple-

menting copper to a fish meal based diet fed to Atlantic

salmon parr affects liver copper and selenium concen-

trations. Aquaculture Nutrition 4, 67–72.

Maage, A.; Julshamn, K., 1993: Assessment of zinc status

in juvenile Atlantic salmon (Salmo salar) by measure-

ment of whole body tissue levels of zinc. Aquaculture

117, 179–191.

Maage, A.; Julshamn, K.; Berge, E., 2001: Zinc gluconate

and zinc sulphate as dietary sources for Atlantic sal-

mon. Aquaculture Nutrition 7, 183–187.

McClain, W. R.; Gatlin, D. M., 1988: Dietary zinc

requirement of Oreochromis aureus and effects of

dietary calcium and phytate on zinc bioavailability.

Journal of the World Aquaculture Society 19, 103–

108.

National Research Council, 1993: Nutrient Requirements of

Fish. National Academy Press, Washington D.C.

O’Dell, B. L., 1984: Bioavailability of trace elements.

Nutrition Reviews 42, 301–308.

Ogino, C.; Yang, G., 1978: Requirement of rainbow trout

for dietary zinc. Bulletin of the Japanese Society of Fisheries

Science 44, 1015–1018.

Paripatananont, T.; Lovell, R. T., 1995a: Chelated zinc

reduces the dietary zinc requirement of channel cat-

fish, Ictalurus punctatus. Journal of Aquatic Animal Health

133, 73–82.

Paripatananont, T.; Lovell, R. T., 1995b: Responses of

channel catfish fed organic and inorganic sources of

zinc to Edwardsiella ictaluri challenge. Journal of Aquatic

Animal Health 7, 147–154.

Paripatananont, T.; Lovell, R. T., 1997: Comparative net

absorption of chelated and inorganic trace minerals in

channel catfish Ictalurus punctatus diets. Journal of the

World Aquaculture Society 28, 62–67.

Ramseyer, L.; Garling, D. Jr; Hill, G.; Link, J., 1999:

Effect of dietary zinc supplementation and phytase pre-

treatment of soybean meal or corn gluten meal on

growth, zinc status and zinc-related metabolism in

rainbow trout, Oncorhynchus mykiss. Fish Physiology and

Biochemistry 20, 251–261.

Rayman, M. P., 2000: The importance of selenium to

human health. The Lancet 356, 233–241.

Richardson, N. L.; Higgs, D. A.; Beames, R. A.; McBride,

J. R., 1985: Influence of dietary calcium, phosphorous,

zinc and sodium phytate level on cataract incidence,

growth and histopathology in juvenile Chinook salmon

(Oncorhynchus tshawytscha). Journal of Nutrition 115,

553–567.

Satoh, S.; Izume, K.; Takeuchi, T.; Watanabe, T., 1987a:

Availability to rainbow trout of zinc contained in vari-



ous types of fish meals. Bulletin of the Japanese Society of

Fisheries Science 53, 1861–1866.

Satoh, S.; Takeuchi, T.; Watanabe, T., 1987b: Availability

to rainbow trout of zinc in white fish meal and of vari-

ous zinc compounds. Bulletin of the Japanese Society of

Fisheries Science 53, 595–599.

Satoh, S.; Poe, W.; Wilson, R. P., 1989: Effect of supple-

mental phytate and/or tricalcium phosphate on weight

gain feed efficiency and zinc content in vertebrae of

channel catfish. Aquaculture 80, 155–161.

Satoh, S.; Porn-Ngam, N.; Takeuchi, T.; Watanabe, T.,

1993: Effect of various types of phosphates on zinc

availability to rainbow trout. Bulletin of the Japanese

Society of Fisheries Science 59, 1395–1400.

Schrauzer, G. N., 2000: Selenomethionine: a review of its

nutritional significance, metabolism and toxicity. Jour-

nal of Nutrition 130, 1653–1656.

Smith, P. K.; Krohn, R. I.; Hermanson, G. T.; Mallia, A.

K.; Gartner, F. H.; Provenzano, M. D.; Fujimoto, E. K.;

Goeke, N. M.; Olson, B. J.; Klenk, D. C., 1985: Mea-

surement of protein using bicinchoninic acid. Analytical

Biochemistry 150, 76–85.

Spry, D. J.; Hodson, P. V.; Wood, C. M., 1988: Relative

contributions of dietary and waterbourne zinc in the

rainbow trout, Salmo gairdneri. Canadian Journal of

Aquaculture Science 45, 32–41.

Storebakken, T.; Shearer, K. D.; Roem, A. J., 2000:

Growth, uptake and retention of nitrogen and phos-

phorous, and absorption of other minerals in Atlantic

salmon Salmo salar fed diets with fish meal and

soy-protein concentrate as the main sources of protein.

Aquaculture Nutrition 6, 103–108.

Tucker, L. A.; Taylor-Pickard, J. A., 2005: Re-Defining Min-

eral Nutrition. Nottingham University Press, UK.

Vallee, B. L.; Falchuk, K. H., 1993: The biochemical basis

of zinc physiology. Physiology Reviews 73, 79–118.

Walter, K.; Schutt, C., 1974:Phosphatases in: Methods of

Enzymatic Analysis 2nd edn, (Vol. 2). Academic Press,

NY. pp. 860–864.

Wang, C.; Lovell, R. T., 1997: Organic selenium sources,

selenomethionine and selenoyeast, have higher bio-

availability than an inorganic selenium source, sodium

selenite, in diets for channel catfish (Ictalurus puncata-

tus). Aquaculture 152, 223–234.

Wang, C.; Lovell, R. T.; Klesius, P. H., 1997: Response to

Edwardsiella ictaluri challenge by channel catfish fed

organic and inorganic sources of selenium. Journal of

Aquatic Animal Health 9, 172–179.

Ward, A. D.; Carter, C. G.; Townsend, A. T., 2005: The

use of yttrium oxide and the effect of faecal collection

timing for determining the apparent digestibility of

minerals and trace elements in Atlantic salmon (Salmo

salar, L.) feeds. Aquaculture Nutrition 11, 49–59.

Wedekind, K. J.; Hortin, E. A.; Baker, D. H., 1992: Meth-

odology for assessing zinc bioavailability: efficacy esti-

mates for zinc-methionine, zinc sulfate, and zinc oxide.

Journal of Animal Science 70, 178–187.

Wekell, J. C.; Shearer, K. D.; Gauglitz, E. J., 1986: Zinc

supplementation of trout diets: tissue indicators of

body zinc status. Progressive Fish Culturist 48, 205–212.



Bioavailability of co-supplemented organic and inorganic zinc and selenium sources in a white...

Documents

Transcript of Bioavailability of co-supplemented organic and inorganic zinc and selenium sources in a white...