Follicle Diameters, Egg Weight, and Egg Production Performance in Old Laying Hens Injected with Growth Hormone and Testosterone

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.