Abstract:
This study investigated how exogenous hormones chan
ge ovary and liver
IGF-I, IGF-IR
and
IGFBP-II
gene expression and egg production performance of
160 laying hens
(HyLine W
-36), at 73
rd
week of age when subcutaneously injected with diff
erent doses of
Growth Hormone (GH) and Testosterone (Ts) as follow
s: Treatment 1 (Tr 1): 100 μL
distilled water (control group); Treatment 2 (Tr 2)
:
Ts 500 μg kg
-1
+GH 50 μg kg
-1
live
weight; Treatment 3 (Tr 3): Ts 500 μg kg
-1
+GH 100 μg kg
-1
live weight, and Treatment 4
(Tr 4): Ts 500 μg kg
-1
+GH 150 μg kg
-1
live weight. The birds were randomly assigned to
the four experimental groups with four replicates o
f 10 birds each, in a completely
randomized design. Fifth-largest-yellow follicle (F
5
) and liver samples were taken just 8
hours after hormone injection. Production performan
ce was measured during fourth and
fifth weeks after hormone injection. Increase in li
ver IGF-I mRNA in Tr4 was
significantly higher than that in Tr 3 and the cont
rol group. The liver
IGF-IR
gene
expressions in all hormone-injected hens were signi
ficantly higher than that in the control
group. The liver
IGFBP-II
mRNAs were significantly higher in Tr 2 and 4 comp
ared with
the control group and Tr 3. The expressions of IGF-
I and
IGF-IR
mRNAs in F
5
wall of
the layers in the control group, Tr 2 and 3, and F
5
IGFBP-II
mRNA in Tr 3 were
significantly increased compared to the other group
s. Ovulation rate in Tr 3 was
significantly higher than other groups. Besides, eg
g mass of Tr 2 and 3 was significantly
more than the control group. Feed intake of Tr 3 si
gnificantly differed from the other
groups. Treatment 4 had significantly higher feed c
onversion ratio compared with Tr 2.
In conclusion, the results show the positive effect
s of the exogenous Ts and GH through
IGF system on reproduction performance in old layin
g hen.
Keywords:
Growth factors, Egg production, Hormone injection,
Insulin-like Physiologically
manipulated spent laying hen
.
