پديد آورندگان :
خيري، روح الله دانشگاه تبريز - گروه علوم دامي , ميرقلنج، علي دانشگاه تبريز - گروه علوم دامي , كيانفر، روح الله دانشگاه تبريز - گروه علوم دامي , جانمحمدي، حسين دانشگاه تبريز - گروه علوم دامي
چكيده لاتين :
Introduction:
Selenium is an essential trace mineral required for normal growth and maintenance in
poultry and specially contributes in
glutathione peroxidase activity, an enzyme transforming the toxic
hydrogen peroxide to harmless water and
oxygen (Rotruck et al. 1973). Selenium may be present in
inorganic or organic
form in the diet and higher absorption being documented for the organic forms
in poultry (Surai and Fisinin 2014)
.
Se
lenium
in its organic form shows higher bioavailability (75.
7%)
than
s
e
lenium
bound in th
e inorganic form (49.9%) (Mahan
et al. 1999).
Organic forms are part of
proteins and include Se
-
Met
hionin
and Se
-
Cys
tein
. Organically bound
s
e
lenium
is mostly used in the
form of Se
-
enriched yeast or other preparations.
In addi
tion to organic Se
lenium
compounds, other
sources have been tested and utilized, such as selenium
-
enriched algae
Scenedesmus quadricauda
,
Se
-
enriched unicellular alga
Chlorella
(Travnicek et al. 2007) and Se
-
enriched yeast (Briens et al.
2013
). E
ffects of
various sources and levels of
selenium
in
the diet on
layers
have been subject of a
number of studies
.
Gjorgovska
et al (2012)
studied various levels of selenium yeast in layers and
reported that
supplementation of 460 mg/kg selenium yeast improved egg production
performance
comparing control birds
. Similar findings have been reported by Heindl et al. (2010), who fed the
layers up to 150 mg/kg selenium yeast.
Attia et al
. (
2010
) reported
increase
in
egg weight
of
laying
hens
fed
organic selenium.
They reported
that
feed conversion ratio
in
laying hens
fed diet
s
containing
250
or
400 mg/kg Selplex, was lower as compared as control birds
.
Some researchers reported that
immune response and
activities of
glutathione peroxidase
in
poultry
plasma increased linearly with
s
e
lenium
concentration
(Rama Rao et al. 2013
; Singh et al. 2006
)
.
Zhang et al (2012) reported that
low
-
selenium
diet caused a decrease in the activities of
total antioxidant cap
acity, superoxide
dismutase,
and glutathione peroxidase
activity
in birds
. The
ir
study
demonstrated that chickens fed
diets deficient in
selenium
exhibited lesions in immune organs, decreased
serum interle
ukin
-
1β,
interleukin
-
2 content,
indicating
that oxi
dative stress inhibited the development of
immune organs
and finally impaired the immune
function of chickens.
Gajcevic
et al (
2009)
reported increase in
glutathione peroxidase activity
in layer hens fed up to 400 mg/kg selenium yeast in diet.
It
has been
documented that l
ayer hens meet some oxidative attacks during
force molting (Siegel 1980),
t
herefore, the aim of this study was to evaluate the effect of
different levels of selenium yeast on egg
production performance, glutathione peroxidase activity and
immune response of laying hens in post
-
molting phase
. Material and
m
ethods:
Eighty W
-
36 leghorn laying hens in post
-
molting phase (78 week) were
assigned to 5 treatments with 4 replications and 4 birds each by employing a completely randomized
design.
After one week adaptation of hens to cages and diets, t
he hens were fed with 5 levels of
selenium yeast
(
Sel
-
plex
)
(
0
,
150
,
300
,
450
and
600
mg/kg) for a period of
4
weeks.
Sel
-
Plex
®
is
Alltech's organic form of selenium
yeast
and each
k
ilogram
of
Sel
-
p
ex
contains1000 mg
selenium
.
All diets were
isocaloric and isonitrogenous
based on corn
-
soybean.
Egg production percent,
egg
weight,
egg mass, feed intake and feed conversion ratio of birds were recorded weekly and reported as hen day basis. E
gg mass
was ca
lculated by
multiplying
the total number of
eggs
laid per hen by
the average
egg
weight
. In the end of experiment, one bird per replicate
with average
cage
weight
selected,
blood samples w
ere
taken
and
glutathione peroxidase (
GPx
)
activity was measured usi
ng
Autoanalyzer system. Another bird per replicate
with average
cage
weight
selected, after injection of
Influenza vaccine in breast muscle, two weeks later, immune response was measured based on
Hemagglutination
-
Inhibition (HI)
Test
.
All data were
analyzed by ANOVA using the procedure
described by the SAS Institute (
200
9
).
Tukey
test was used to
determine the significant differences
between treatment means. Results and
d
iscussion
: Results showed that using 300 and 450 mg/kg selenium yeast in
post
-
molting diet
of layers
, significantly increased egg production rate as compared with control
ones
(P<0.01). Similar findings have been reported by Gjorgovska et al (2012), who fed the layers different
levels of selenium yeast and reported that supplem
entation of 460 mg/kg selenium yeast improved
egg production performance as compared as control birds, but some researchers (Leeson et al. 2008)
reported that supplementation
with
selenium yeast did not affect egg production performance.
In this
experiment
, a
ddition of 600 mg/kg selenium yeast, caused to negative effect on egg production
performance as compared as other groups, probably due to toxic effects of organic selenium in higher
dosage. The reason for better performance in birds fed 300 and 450 mg/k
g selenium yeast was
improved immune function and better antioxidant status in those birds.
E
gg weight of birds
fed diets
containing
600 mg/kg selenium yeast, increased significantly (P<0.05) as compared as control birds.
This result was in accordance to
Attia et al
. (
2010
) who reported
increase
in
egg weight
of
laying
hens
fed diet containing
higher than
400 mg/kg Selplex. Linoleic acid is
one of the
key factor
s
in
determining egg yolk size and egg weight and any factor oxidizing this fatty acid, may be a
ffect egg
weight (Balnave 1971). Sel
-
plex as a strong antioxidant has important role in stabilizing the
unsaturated fatty acids such as linoleic acid, therefore can affect egg yolk size and egg weight. E
gg
mass
was calculated by
multiplying
the total numbe
r of
eggs
laid per hen by the average
egg weight
,
therefore egg production and egg weight may affect egg mass. In this study, there were no significant
differences (P<0.05) between egg mass and feed intake of birds fed different diets during total period,
but feed conversion ratio of birds fed 300 and 450 mg/kg selenium yeast, were significantly lower as
compared with the control birds(P<0.05).
These results were in accordance to
Attia et al
. (
2010
) who
reported
that
feed conversion ratio
in
laying hens
fed
diet containing
250 and
400 mg/kg Selplex, was
lower as compared as control birds.
At the end of experiment, the glutathione peroxidase activity and
antibody titer against Influenza virus increased significantly
in birds receiving 300 mg/kg selenium
yeast
or higher levels (P<0.
05)
.
In accordance
with this study, Savaram et al (2013) showed
improvement in immune response of broiler chickens fed 400 mg/kg selenium yeast and also
Gajcevic
et al (2009) reported increase in glutathione peroxidase activity
in
layer hens fed up to 400 mg/kg
Sel
-
plex in diet.
B
etter
production
performance in birds fed 300 and 450 mg/kg selenium yeast was
due to
improved immune function and better antioxidant status in
this study
.
Conclusion:
It is concluded that use of 300 mg/kg
selenium yeast could
improve
egg production rate,
glutathione peroxidase activity and immune response of la
ying hens in post
-
molting phase
.
