Ovary and Liver IGF-I, IGF-IR and IGFBP-II Gene Expressions and Reproduction Performance of Old Lay ing Hens Injected with Growth Hormone and Testosterone

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 .