ovary and liver igf-i, igf-ir and igfbp-ii gene expressions and reproduction performance of old laying hens injected with growth hormone and testosterone

This study investigated how exogenous hormones change ovary and liver igf-i, igf-ir and igfbp-ii gene expression and egg production performance of 160 laying hens (hyline w-36), at 73rd week of age when subcutaneously injected with different doses of growth hormone (gh) and testosterone (ts) as follows: 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 of 10 birds each, in a completely randomized design. fifth-largest-yellow follicle (f5) and liver samples were taken just 8 hours after hormone injection. production performance was measured during fourth and fifth weeks after hormone injection. increase in liver igf-i mrna in tr4 was significantly higher than that in tr 3 and the control group. the liver igf-ir gene expressions in all hormone-injected hens were significantly higher than that in the control group. the liver igfbp-ii mrnas were significantly higher in tr 2 and 4 compared with the control group and tr 3. the expressions of igf-i and igf-ir mrnas in f5 wall of the layers in the control group, tr 2 and 3, and f5 igfbp-ii mrna in tr 3 were significantly increased compared to the other groups. ovulation rate in tr 3 was significantly higher than other groups. besides, egg mass of tr 2 and 3 was significantly more than the control group. feed intake of tr 3 significantly differed from the other groups. treatment 4 had significantly higher feed conversion ratio compared with tr 2. in conclusion, the results show the positive effects of the exogenous ts and gh through igf system on reproduction performance in old laying hen.