2605
2008 Poultry Science 87:2605–2612 doi:10.3382/ps.2008-00174 Key words: selenium, broiler breeder, laying hen, production, glutathione peroxidase
ABSTRACT Two experiments were carried out with broiler breeders (experiment 1) and laying hens (experi- ment 2) to study the effects of Se sources, in interaction with dietary level of Se or dietary fats on performance, Se incorporation into tissues (blood, liver, breast mus- cle, and egg) and eggs, hatchability, and glutathione peroxidase (GPX) activities in tissues and blood. Both experiments involved a 3 × 2 factorial arrangement of 3 Se sources (selenite, Se yeast, or B-Traxim Se) and ei- ther 2 levels of each source (0.1 or 0.3 mg/kg) or 2 fats (fresh or oxidized). Egg production was not affected by Se source or dietary fat in both experiments. Egg production was greater (P < 0.01) in breeder hens fed 0.3 mg/kg of Se in experiment 1. Hatchability of eggs from hens fed 0.1 mg/kg of Se was lower (P < 0.05) in hens fed Se yeast, whereas from hens fed 0.3 mg/kg of Se, it was comparable across treatments. Selenium in egg, liver, and breast muscle was greater (P < 0.01 or
<0.05) in hens fed the greater concentration of Se. Eggs from breeder hens fed organic Se sources had greater (P
< 0.01) Se content than those of inorganic source. Egg albumen from breeder fed Se yeast had the greatest Se (P < 0.01), whereas egg yolk from hens fed B-Traxim Se had the greatest Se (P < 0.05). These parameters were affected by interaction between dietary Se level and source (P < 0.01 or < 0.05). Selenium contents in liver and breast muscle were greater (P < 0.01) in hens fed Se yeast compared with hens fed other sources of Se. In experiment 1, liver GPX was greater (P < 0.01) in hens fed selenite or Se yeast, whereas plasma GPX was greater (P < 0.01) in hens fed selenite compared with B-Traxim Se or Se yeast. Supplementation with oxidized fat increased (P < 0.05) GPX in blood and liv- er. B-Traxim Se decreased (P < 0.05) malondialdehyde content in breast muscle of layers. It is concluded that broiler breeders require supplementation of 0.3 mg/kg of Se, and that there are numerous measurable advan- tages in using organic rather than inorganic sources for both breeders and layers.
for Broiler Breeders and Layer Hens
S. Leeson,*1 H. Namkung,* L. Caston,* S. Durosoy,† and P. Schlegel†
*Department of Animal and Poultry Science, University of Guelph, Guelph, Ontario, Canada N1G 2W1;
and †Pancosma SA, Voie-des-Traz 6, 1218 Le Grand Saconnex, Geneva, Switzerland
INTRODUCTION
Selenium is an integral part of the enzyme glutathi- one peroxidase (GPX), which serves as an antioxidant enzyme that helps to control levels of hydrogen perox- ide and lipid peroxides that are produced during nor- mal metabolic activity (Rotruck et al., 1973). Dietary supplementation of Se usually results in increased egg Se content (Ort and Latshaw, 1978; Sirichakwal et al., 1984; Pappas et al., 2005) and GPX activity in tissues (DeVore et al., 1983; Payne and Southern, 2005). Sup- plementation of the hen’s diet with Se directly influ- ences the activity of GPX in the newly hatched chicks (Surai, 2000) and increases hatchability of fertile eggs
from hens fed such supplements (Cantor and Scott, 1974; Latshaw and Osman, 1974).
Generally, the inorganic salt of Se (sodium selenite) is added to the diets of broiler chickens at a concentra- tion of 0.3 mg/kg. Over the last few years, there has been interest in replacing part or all of this inorganic source with organic Se. Cantor et al. (1982) reported an organic form of Se to be more bioavailable than was sodium selenite. It has been reported that dietary or- ganic Se increases the Se content of eggs (Cantor et al., 2000; Payne et al., 2005) and developing embryos (Pa- ton et al., 2002). Presently, the most common source of organic Se is a Se yeast. B-Traxim Se (Pancosma SA, Geneva, Swizerland) is a newly developed organic Se product using soybean peptides as the ligand. The aim of this study was to investigate the effects of Se sources, in interaction with dietary level of Se or dietary fats (fresh or oxidized) on performance, Se incorporation into certain poultry tissues and eggs, hatchability, and
Received April 28, 2008.
Accepted August 7, 2008.
1 Corresponding author: sleeson@uoguelph.ca
©2008 Poultry Science Association Inc.
GPX in tissues and eggs in broiler breeder hens and laying hens.
MATERIALS AND METHODS
Two experiments were conducted to study the effects of Se sources on the performance and oxidation sta- tus of broiler breeder and layer hens. In experiment 1, forty-eight 50-wk-old broiler breeder hens (Ross 308) were randomly assigned to 6 diet treatment groups.
Treatments (Table 1) consisted of a 3 × 2 factorial arrangement of 3 Se sources (selenite, Se yeast, or B- Traxim Se) and 2 levels (0.1 or 0.3 mg/kg) of each Se source. Each diet was fed to 8 replicate individually caged broiler breeder hens for 45 d. All birds were in- seminated weekly with 0.1 mL of pooled semen collect- ed from breeder males fed 0.3 mg/kg of sodium selenite (Pancosma SA).
Eggs were collected during d 30 to 35 for measurement of egg weight and eggshell deformation as a measure of shell strength, and from d 46 for yolk Se content. Egg production was monitored throughout the trial. Hatch- ability was measured from all eggs produced between d 36 and 45. Blood was collected by venous puncture for assay of GPX in plasma at d 46, and then birds were humanely killed for sampling of breast muscle and liver.
Selenium assays were conducted on egg yolk and albu- men, blood plasma, breast muscle, and liver.
In experiment 2, forty-eight 48-wk-old hens (Lohman White) were randomly assigned to 6 treatment groups.
Treatments consisted of a 3 × 2 factorial arrangement of 3 Se sources (selenite, Se yeast, or B-Traxim Se, all added at 0.3 mg/kg) and 2 grades of dietary canola oil (fresh or rancid). Composition and calculated nutrient contents of diets for experiment 2 are given in Table 2.
Each diet was fed to 8 replicate individually caged laying
hens for 40 d. The peroxide values for fresh and rancid oil used for this experiment were 2.5 and 60.9 mEq/kg of fat, respectively. Rancidity was achieved by placing a subsample of the canola oil in an open container in direct sunlight for 48 h. Egg weight and eggshell defor- mation were measured at d 5 to 7 and d 38 to 40. Egg production was monitored throughout the trial. Blood sampled at d 5 and 40 was assayed for Se content and GPX activity. Plasma samples separated from blood at d 40 were also assayed for Se. Liver and breast mus- cle were collected at d 40 after blood collection. Liver samples were assayed for Se, GPX activity, and malon- dialdehyde (MDA) as an indicator of lipid oxidation.
Breast muscle samples were assayed for MDA. Yolks from eggs collected at d 40 were also assayed for Se and MDA. The trials were conducted at the Arkell Poultry Research Station under the guidelines of the Canadian Council on Animal Care and with the approval of the University of Guelph’s Animal Care Services. The data were considered by a 2-factor factorial analysis (2 × 3) where the main effects were either 2 levels of Se (0.1 or 0.3 mg/kg) or dietary fats (fresh or rancid fats), and sourse of Se (selenite, Se yeast, or B-Traxim Se). Data were subjected to an ANOVA procedure (GLM, SAS Institute Inc., Cary, NC) considering main effects and their interaction. Those response variables resulting in a significant F-test were further analyzed using Tukey’s test. Significance was accepted at P < 0.05.
In both experiments, Se concentration of whole blood, tissue samples, and extracts was determined by a semi- automated fluorometric assay (Brown and Watkinson 1977). In experiments 1 and 2, GPX activity was mea- sured in blood, liver, and breast muscle. Blood samples were centrifuged for 15 min at 3,000 × g and 4°C, and then plasma was collected and stored at −80°C un- til analysis. Livers were perfused in situ with ice-cold KCl (0.15 mol/L) and homogenized with 50 mM Tris- Table 1. Diet composition (g/kg, experiment 1)
Item
Sodium selenite Se yeast B-Traxim Se
0.1 mg/kg 0.3 mg/kg 0.1 mg/kg 0.3 mg/kg 0.1 mg/kg 0.3 mg/kg
Corn 580.00 580.00 580.00 580.00 580.00 580.00
Wheat shorts 84.80 83.80 84.80 83.80 85.29 85.02
Soybean meal 210.00 210.00 210.00 210.00 210.00 210.00
Limestone 79.00 79.00 79.00 79.00 79.00 79.00
Dicalcium phosphate 17.00 17.00 17.00 17.00 17.00 17.00
Animal-vegetable fat 20.00 20.00 20.00 20.00 20.00 20.00
Salt 3.00 3.00 3.00 3.00 3.00 3.00
dl-Methionine 0.70 0.70 0.70 0.70 0.70 0.70
Vitamin-mineral premix 5.00 5.00 5.00 5.00 5.00 5.00
Sodium selenite premix1 0.50 1.50 0.00 0.00 0.00 0.00
Se yeast premix1 0.00 0.00 0.50 1.50 0.00 0.00
B-Traxim Se premix1,2 0.00 0.00 0.00 0.00 0.01 0.03
Total, g 1,000 1,000 1,000 1,000 1,000 1,000
Analyzed nutrient composition
Se, mg/kg 0.18 0.32 0.12 0.48 0.21 0.42
CP, % 15.9 16.9 17.4 17.0 17.8 16.9
Crude fat, % 3.7 3.9 3.8 3.8 3.6 3.7
1The Se premixes were made by premixing 100 g of Se source with 900 g of ground corn.
2Pancosma SA, Geneva, Switzerland.
HCl buffer (pH 7.0). Homogenates were centrifuged at 13,000 × g for 15 min at 4°C. Supernatants were stored at −80°C until analysis. Glutathione peroxidase activ- ity in the supernatants and plasma was determined us- ing a diagnostic kit (CGP1, Sigma, St. Louis, MO).
The protein in supernatants was determined spectro- photometrically using a bicinchoninic acid protein as- say kit (BCA-1 and B-9643, Sigma). One GPX enzyme activity unit equals 1 micromole of glutathione oxidized per minute and per milligram of protein. In experiment 2, rancidity of dietary oil was measured by the method of AOAC (1990) measuring peroxide value, and MDA content in liver was measured for lipid oxidation of liver (Squires et al., 1991).
RESULTS
The composition and nutrient contents of diets for experiments 1 and 2 are detailed in Tables 1 and 2, re- spectively. Analyzed Se contents in both diets for both experiments were slightly greater than calculated val- ues. The peroxide values of canola oil used for experi- ment 2 were 2.5 mEq/kg of fat for fresh oil and 60.9 mEq/kg of fat for oxidized oil, respectively (Table 2).
In experiment 1, egg production, egg weight, and eggshell deformation of broiler breeders are presented in Table 3. Egg production was increased (P < 0.01) by using the greater concentration of Se in the diet but did not differ by source of Se, and there was no interac- tion between concentration and source of Se in the diet.
Egg weight and eggshell deformation were unaffected by concentration or source of Se in the diet (P > 0.05).
Hatchability was not affected by dietary Se concen- tration or source. However, hatchability was affected by interaction between dietary Se concentration and source (P < 0.05); hatchability of eggs from hens fed Se
yeast was lowest in hens fed 0.1 mg/kg of Se, whereas hatchability of eggs from hens fed 0.3 mg/kg of Se was comparable (but lower) across all treatments.
Plasma Se content was not affected by dietary Se concentration or source (Table 4). Selenium content of eggs, liver, and breast muscle was affected by interac- tion between dietary Se concentration and source (P
< 0.01 or 0.05). Selenium contents of eggs, liver, and breast muscle were greater (P < 0.01 or 0.05) in hens fed the greater concentration of Se. Selenium content in yolk was greatest (P < 0.01) in hens fed B-Traxim Se, whereas Se content in albumen was greatest (P < 0.01) in hens fed Se yeast. However, there was no difference in combined Se contents of yolk plus albumen for hens fed Se yeast or B-Traxim Se. Selenium content in breast muscle was greater in hens fed Se yeast compared with hens fed other sources of Se (P < 0.01).
Glutathione peroxidase activity in liver and plasma was affected (P < 0.01) by Se source but not by concen- tration (Table 5). Activity of GPX in liver was greater in hens fed selenite or Se yeast, and in plasma was greater in hens fed selenite compared with B-Traxim Se or Se yeast; GPX in breast muscle was not different among treatments.
In experiment 2, feed intake was not different across treatments although hens fed oxidized oil ate a little more feed than hens fed fresh oil (100.7 vs. 96.7 g). Egg weight and egg production were not different across di- etary treatments. There was an interaction (P < 0.05) between Se sources and dietary fat for egg deformation in the first week. Egg deformation was greater (poorer eggshell quality) in hens fed fresh oil with sodium sel- enite and Se yeast as Se sources, whereas egg deforma- tion in hens fed B-Traxim Se was greater in birds fed rancid oil vs. fresh oil. However, egg deformation in wk 6 was not affected by interaction between Se source and dietary oil freshness.
Table 2. Diet composition (g/kg, experiment 2)
Item
Fresh oil Rancid oil
Sodium selenite Se yeast B-Traxim Se Sodium selenite Se yeast B-Traxim Se
Corn 582.00 582.00 582.00 582.00 582.00 582.00
Wheat shorts 0.50 0.50 1.72 0.50 0.50 1.72
Soybean meal 248.00 248.00 248.00 248.00 248.00 248.00
Limestone 108.00 108.00 108.00 108.00 108.00 108.00
Dicalcium phosphate 10.00 10.00 10.00 10.00 10.00 10.00
Fresh canola oil1 40.00 40.00 40.00 0.00 0.00 0.00
Rancid canola oil1 0.00 0.00 0.00 40.00 40.00 40.00
Salt 3.00 3.00 3.00 3.00 3.00 3.00
dl-Methionine 2.00 2.00 2.00 2.00 2.00 2.00
Vitamin-mineral premix 5.00 5.00 5.00 5.00 5.00 5.00
Selenite premix2 1.50 0.00 0.00 1.50 0.00 0.00
Se yeast premix2 0.00 1.50 0.00 0.00 1.50 0.00
B-Traxim Se premix2,3 0.00 0.00 0.28 0.00 0.00 0.28
Total, g 1,000.00 1,000.00 1,000.00 1,000.00 1,000.00 1,000.00
Analyzed Se, mg/kg 0.40 0.38 0.30 0.40 0.36 0.41
1Peroxide values of fresh and rancid canola oil were 2.5 and 60.9 mEq/kg of fat, respectively.
2The Se premixes were made by premixing 100 g of Se source with 900 g of ground corn.
3Pancosma SA, Geneva, Switzerland.
Selenium contents of blood, liver, and eggs are shown in Table 6. Selenium content in whole blood at d 5 was not affected by main effects of dietary treatments, whereas at d 40, hens fed Se yeast had greater (P <
0.01) Se contents in whole blood and plasma than hens fed other sources of Se. However, plasma Se in hens fed Se yeast was not different from that in hens fed B-Traxim Se. Rancidity of dietary oil did not affect Se content in whole blood or plasma. Liver Se content was not different between treatments. Total egg Se content was greater (P < 0.01) in hens fed Se yeast and B-
Traxim Se compared with Se selenite. When yolk and albumen were separated, yolk Se content was increased (P < 0.01) with B-Traxim Se, whereas albumen Se con- tent was increased (P < 0.01) in hens fed Se yeast when compared with sodium selenite.
Activity of GPX in blood and liver was not affected by Se sources (Table 7). However, GPX in whole blood and liver at 40 d were greater (P < 0.05) in hens fed rancid oil than in hens fed fresh oil. Sources of oils and Se did not affect MDA content in liver and yolk (Table 8), whereas MDA contents in breast muscle were low- Table 3. Egg production, egg weight, and eggshell deformation of broiler breeder hens fed different concentrations and sources of Se (experiment 1)
Item Se level (mg/kg) Egg production (%) Egg weight (g) Eggshell
deformation (μm) Hatchability (% fertile eggs) Se source
Sodium selenite 0.1 68.3 69.8 26.8 96.4
0.3 69.5 68.5 27.0 82.5
Se yeast 0.1 63.5 68.1 26.4 74.3
0.3 74.0 65.9 29.0 87.4
B-Traxim Se1 0.1 63.0 69.1 25.2 95.9
0.3 73.5 69.3 26.3 80.2
Pooled SEM 3.3 1.3 1.0 6.0
Main effects Se source
Sodium selenite 68.9 69.2 26.9 89.4
Se yeast 68.8 67.0 27.7 80.9
B-Traxim Se 68.3 69.2 25.8 87.5
Se level, mg/kg
0.1 64.9B 68.9 26.2 88.6
0.3 72.3A 67.9 27.4 83.4
Se source NS NS NS NS
Se level ** NS NS NS
Source × level NS NS NS *
A,BValues within columns with no common superscript differ (P < 0.01).
1Pancosma SA, Geneva, Switzerland.
*P < 0.05; **P < 0.01; NS: P > 0.05.
Table 4. Selenium content in plasma, egg, and tissue of broiler breeder hens fed different levels and sources of Se (experiment 1)
Item Se level
(mg/kg) Plasma
(μg/mL) Yolk
(μg/egg) Albumen
(μg/egg) Yolk + albumen
(μg/whole egg) Liver
(μg/g) Breast muscle (μg/g) Se source
Sodium selenite 0.1 0.168 7.16C 2.43D 9.58D 0.41B 0.165B
0.3 0.178 7.68C 2.81C 10.44CD 0.46AB 0.164B
Se yeast 0.1 0.148 7.22C 3.32B 10.44CD 0.44B 0.165B
0.3 0.190 7.80BC 4.81A 13.01A 0.53A 0.205A
B-Traxim Se1 0.1 0.152 8.58AB 2.38D 10.90BC 0.48AB 0.156B
0.3 0.153 8.82A 2.91BC 11.73AB 0.45 AB 0.154B
Pooled SEM 0.012 0.29 0.11 0.32 0.19 0.01
Main effects Se source
Sodium selenite 0.173 7.40B 2.60B 10.01 B 0.43b 0.164B
Se yeast 0.169 7.49B 4.02A 11.73A 0.48a 0.185A
B-Traxim Se 0.152 8.70A 2.66B 11.31A 0.47ab 0.155B
Se level, mg/kg
0.1 0.156 7.65b 2.69B 10.31B 0.44b 0.162B
0.3 0.173 8.13a 3.54A 11.80A 0.48a 0.174A
Se source NS ** ** ** * **
Se level NS * ** ** * **
Se source × level NS NS ** * * **
a,b, A–DValues within each column with no common superscript differ (P < 0.05 and P < 0.01, respectively).
1Pancosma SA, Geneva, Switzerland.
*P < 0.05; **P < 0.01; NS: P > 0.05.
er in hens fed organic Se sources compared with hens fed inorganic Se; hens fed B-Traxim Se had the lowest MDA content in breast muscle.
DISCUSSION
Using inorganic versus organic Se had no effect on egg production or egg weight of broiler breeders or lay- ers, which is in agreement with the previous findings of Cantor et al. (2000) and Utterback et al. (2005).
It should also be noted that the relatively short time frame of the 2 current experiments (40 to 45 d) may be inadequate for accurate assessment of an effect on egg production, although any effects on egg weight should be realized within this time frame. Payne et al. (2005) reported a trend for an increase in egg production as di- etary Se from selenite or Se yeast increased from 0.1 to 0.6 mg/kg, although this situation was associated with a corresponding reduction in feed intake. The current data and that of Utterback et al. (2005) do not support Table 5. Glutathione peroxidase activity (mU/mg of protein) in liver, plasma, and breast muscle of
broiler breeder hens fed different levels and sources of Se (experiment 1)
Item Se level (mg/kg) Liver Plasma Breast muscle
Se source
Sodium selenite 0.1 79.88A 173.00A 40.07
0.3 70.88AB 166.00A 40.00
Se yeast 0.1 79.63A 116.00B 42.63
0.3 77.38A 106.86B 38.80
B-Traxim Se1 0.1 55.75B 108.57B 35.63
0.3 62.75AB 111.00B 41.47
Pooled SEM 4.34 14.05 4.45
Main effects Se source
Sodium selenite 75.38A 169.50A 40.71
Se yeast 78.50A 111.43B 40.03
B-Traxim Se 59.25B 109.87B 38.55
Se level, mg/kg
0.1 71.75 128.26 39.76
0.3 70.33 123.30 39.96
Se source ** ** NS
Se level NS NS NS
Se source × level NS NS NS
A,BValues within each column with no common superscript differ (P < 0.01).
1Pancosma SA, Geneva, Switzerland.
**P < 0.01; NS: P > 0.05.
Table 6. Selenium content in blood, plasma, yolk, and albumen of laying hens fed different sources of Se with fresh or rancid canola oil (experiment 2)
Item Oil
Day 5 Day 40
Blood
(μg/mL) Blood
(μg/mL) Plasma
(μg/mL) Liver
(μg/g) Yolk
(μg/egg) Albumen
(μg/egg) Yolk + albumen (μg/egg) Se source
Sodium selenite Fresh 0.233b 0.177BC 0.150b 0.551 4.89B 1.66B 6.55D
Rancid 0.243b 0.169C 0.151b 0.495 6.08B 1.77B 7.85BCD
Se yeast Fresh 0.234b 0.209A 0.180a 0.739 6.04B 3.66A 9.70ABC
Rancid 0.269a 0.208A 0.184a 0.565 6.51B 3.68A 10.19AB
B-Traxim Se1 Fresh 0.255ab 0.193AB 0.173ab 0.628 10.24A 1.90B 12.14A
Rancid 0.240b 0.180BC 0.170ab 0.501 5.18B 1.57B 6.75CD
Pooled SEM 0.009 0.007 0.008 0.085 0.691 0.134 0.662
Main effects Se source
Sodium selenite 0.238 0.173B 0.151B 0.523 5.49b 1.71B 7.20B
Se yeast 0.253 0.208A 0.182A 0.652 6.26ab 3.67A 9.93A
B-Traxim Se 0.248 0.186B 0.172A 0.564 7.35a 1.71B 9.06A
Oil Fresh 0.241 0.193 0.166 0.639 6.86 2.49 9.35
Rancid 0.250 0.185 0.168 0.520 5.89 2.31 8.20
Se source NS ** ** NS * ** **
Oil NS NS NS NS NS NS NS
Se source × oil * NS NS NS ** NS **
a,b, A–DValues within each column with no common superscript differ (P < 0.05 and P < 0.01, respectively).
1Pancosma SA, Geneva, Switzerland.
*P < 0.05; **P < 0.01; NS: P > 0.05.
the contention that either Se source or concentration affect feed intake assuming diet adequacy. When breed- ers were fed diets with just 0.1 mg/kg of either organic or inorganic sources of Se, there was a reduction in egg production compared with feeding at 0.3 mg/kg. Feed intake was not measured in experiment 1; breeders were offered a set amount of feed daily (150 g), and although there was no meaningful accumulation over time, it is not known if variable daily feed intake was a factor precipitating change in egg production.
Although neither concentration nor source of Se fed to breeders affected hatchability of fertile eggs, an in- teraction was observed. With supplementation at 0.1 mg/kg, lower hatchability was observed in eggs from birds fed Se yeast. Pappas et al. (2006) showed no dif- ference in hatch of eggs from hens fed 0.1 vs. 1 mg/
kg, although Ort and Latshaw (1978) showed reduced hatch only when very high concentrations of selenite were supplemented. These results relate to hatch of fer- tile eggs and are assumed to be independent of any Table 7. Glutathione peroxidase activity (mU/mg of protein) in whole blood and liver of laying hens
(experiment 2)
Item Oil
Day 5 Day 40
Blood Blood Liver
Se source
Sodium selenite Fresh 211.6 265.4 103.1
Rancid 183.5 351.4 126.4
Se yeast Fresh 192.3 221.6 103.8
Rancid 213.6 337.5 126.2
B-Traxim Se1 Fresh 187.3 278.3 129.0
Rancid 193.3 259.1 154.4
Pooled SEM 18.3 32.9 13.2
Main effects Se source
Sodium selenite 197.6 311.3 115.5
Se yeast 203.7 279.6 114.2
B-Traxim Se 190.3 268.7 141.6
Oil
Fresh 197.3 254.7b 111.6b
Rancid 196.8 316.0a 135.2a
Se source NS NS NS
Oil NS * *
Se source × oil NS NS NS
a,bValues within each column with no common superscript differ (P < 0.05).
1Pancosma SA, Geneva, Switzerland.
*P < 0.05; NS: P > 0.05.
Table 8. Malondialdehyde content (ng/g) in liver, breast muscle, and egg yolk of laying hens (experi- ment 2)
Item Oil Liver Breast muscle Egg yolk
Se source
Sodium selenite Fresh 350 384ab 132
Rancid 408 353abc 112
Se yeast Fresh 424 409a 130
Rancid 385 265c 104
B-Traxim Se1 Fresh 350 295bc 115
Rancid 370 254c 126
SEM 34 34 10
Main effects Se source
Sodium selenite 381 368a 123
Se yeast 405 337ab 119
B-Traxim Se 359 275b 121
Oil
Fresh 375 362 126
Rancid 389 291 115
Se source NS * NS
Oil NS NS NS
Se source × oil NS NS NS
a–cValues within each column with no common superscript differ (P < 0.05).
1Pancosma SA, Geneva, Switzerland.
*P < 0.05; NS: P > 0.05.
attributes of the sperm used in insemination. Surai et al. (1998) observed increased GPX and associated en- hanced protection against lipid peroxidation in semen of cockerels fed organic Se, so male nutrition can af- fect hatchability per se. There does not seem to be any information available on the effect of breeder hen Se status on semen capacitation and viability during stor- age in the oviduct.
The major difference between the 2 sources of or- ganic Se used in this study was on the subsequent ac- cumulation of Se in various components of the egg and other tissues. The Se yeast, which is assumed to be predominantly selenomethionine, appeared to be pref- erentially deposited in proteins as evidenced by greater levels in both albumen and breast muscle. The Se from B-Traxim Se, which predominantly comprises di- and tri- peptide ligands, accumulated to a greater extent in lipid-associated components such as yolk. Paton et al. (2002) reported a linear increase in egg Se when birds were fed either selenite or organic Se with pro- portionally more accumulating in the yolk. Preferen- tial deposition of Se in yolk may be a consequence of mineral-binding lipoproteins deposited during yolk ac- cretion (Richards, 1977; Miles, 2000). Latshaw (1975), Utterback et al. (2005), and Pappas et al. (2006) also reported greater egg Se accumulation when selenom- ethionine or other organic Se products were used com- pared with selenite. At this time it is unclear whether deposition of selenomethionine or Se proteinates is a direct consequence of the need for Se as such, or that alternatively Se deposition is a simple consequence of the deposition of the associated methionine or proteins and peptides. Broiler meat also seems to accumulate Se in response to feeding level (Bou et al. 2005), although there is less information available on bioefficacy of vari- ous Se sources.
The effect of dietary Se and Se source had inconsis- tent effects on GPX activity in broiler breeders and lay- ers used in the 2 experiments. Because Se is a compo- nent of GPX, the classical assumption is that increased availability of metabolic Se will lead to increased levels of GPX, and this parameter is often used in bioeffi- cacy studies (Whanger and Butler, 1988; Humaloja and Mykkanen, 1986; Mahan et al. 1999), although incon- sistencies are noted. In experiment 1, a Se concentra- tion of 0.1 or 0.3 mg/kg had no effect on GPX activity in liver, plasma, or breast muscle. However, using either organic source of Se resulted in a highly significant de- cline in plasma GPX (Table 5), and supplementation with B-Traxim Se resulted in less liver GPX compared with using selenite. There was also a numerical decline in blood GPX when layers were sampled after 40 d fol- lowing feeding of both sources of organic Se. Whanger and Butler (1988) reported no differences in the GPX activity in tissues of rats fed Se as either selenomethione or selenite. Payne and Southern (2005) also reported no difference in GPX activity of plasma of broilers fed bas- al or experimental diets supplemented with 0.3 mg/kg of Se as sodium selenite to a basal diet that contained
0.12 mg/kg of Se. Mahan and Parrett (1996) and Ma- han et al. (1999) reported that pigs fed organic Se (0.1 mg/kg) had serum GPX values that tended to be lower than those of pigs fed an inorganic Se source, but GPX activities in both groups were similar when greater di- etary Se levels were utilized. Lane et al. (1991) reported that rat pups given intraperitoneal selenite (3 μg/kg of BW) had greater liver and kidney GPX activity than pups given the same amount of Se as selenomethionine.
Using 75Se, Beilstein and Whanger (1988) reported that tissue GPX activities were not different in rats fed di- etary Se as either selenite or selenomethionine, but that the proportion of Se as GPX in tissues was different between Se sources. Surai (2000) reported that chicks and eggs of hens fed Se-supplemented diets had greater GPX, although the level of supplementation had only a minimal effect. There is some suggestion, therefore, that GPX activity is less in certain tissues when organic rather than inorganic Se is used as a feed supplement, and this seems contrary to the general assumption that organic sources are more bioavailable. The egg and tis- sue accumulation of Se is greater when organic sources are used, so it cannot be argued that organic sources are less available to the various tissues.
A more logical interpretation is that with better oxi- dative stability there is, in fact, less need for synthesis of GPX, so lower levels are indicative of better health status. Certainly, in experiment 2 where rancid fat was used, there is a classical increase in GPX noted in both blood and liver. There was about a 20% increase in GPX activity in blood and liver after laying hens had been fed diets containing rancid fat for 40 d (Table 7), with this effect being independent of Se source. Vilas et al. (1976) reported that feeding rats oxidized oil did not affect GPX activity in the plasma, whereas GPX of intestinal mucosa was significantly increased, implying that GPX might be involved in protecting the mucosa from damage caused by peroxides in the diets. Eder et al. (2002) reported that Se concentrations in liver and plasma and the activity of GPX in plasma of rats fed diets with 70 μg of Se/kg with oxidized fat were actu- ally lower than those of rats fed the corresponding diets with fresh fat. Reddy and Tappel (1974) suggested that GPX activity in various tissues of the rat in response to rancid fat are likely influenced by the level of Se supple- mentation, and that generalizations therefore can be misleading. Engberg et al. (1996) reported that GPX activity in the liver of broilers was not different when using fresh or oxidized oil. Chen (1973) reported that TBA values in liver of rats fed 1 vs. 0 mg/kg of Se as sodium selenite, selenomethionine, or selenocystine was significantly lower, although there was no difference be- tween Se sources. DeVore et al. (1983), on the other hand, reported that GPX in various muscles of chickens fed Se-supplemented diets was greater than in muscles from the nonsupplemented birds, and the greater GPX was accompanied by lower TBA values in meat. Al- though GPX in breast muscle was not measured in the current experiment, low MDA in breast muscle of hens
fed organic forms of Se might be associated with great- er GPX activity.
It is concluded that organic sources of Se result in greater deposition of Se in eggs and various tissues.
The structure of the organic Se seems to dictate depo- sition in proteins or lipoproteins or, alternatively, as a component of an amino acid or as Se itself. There is an indication of lower GPX activity in birds fed organic Se, and this is interpreted at this time as being indica- tive of improved oxidative stability and less need for enzyme intervention.
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