Abstract:
Hen aging is accompanied by a disruption of product
ive performance, namely, egg
production. The current study was carried out to in
vestigate how exogenous Growth
Hormone (GH) and Testosterone (Ts) change diameters
of hierarchal follicles, egg weight,
and egg production performance of old laying hens i
n the late phase of production. To
this end, 160 HyLine W
-36 laying hens (aged 73 weeks), were injected (sin
gle injection)
with GH and Ts as follows: Treatment 1: 100 μL dist
illed water (control group);
Treatment 2: 500 μg Ts kg
-1
Body-Weight (BW)+50 μg GH kg
-1
body-weight; Treatment
3: 500 μg Ts kg
-1
BW
+100 μg GH kg
-1
BW, and Treatment 4: 500 μg Ts kg
-1
BW
+150 μg
GH kg
-1
BW
. The experiment had four replicates and 10 birds i
n each replicate in a
completely randomized design. The diameters of Smal
l White Follicle (SWF), Large
White Follicle (LWF), the First (F
1
), Second (F
2
) and Third (F
3
) largest yellow follicles in
treatment 3 were significantly larger than in the c
ontrol group, in the second week after
the injection. Hen-Day Egg Production percent (HDEP
), egg mass, and Feed Intake (FI)
of treatment 3 were significantly higher than all o
ther groups, during the second week
after the injection; besides, HDEP and FI in treatm
ent 4 were significantly more than in
the control group. These results suggest that in ol
d laying hen, GH and Ts may positively
influence follicular diameters and egg production p
erformance.
Keywords:
Egg parameters, Hen-day egg production, HyLine W-3
6 laying hens.
