Dynamic changes in insulin-like growth factor binding protein expression occur between embryonic and early post-hatch...

Area of Science:

• Animal Science
• Developmental Biology
• Molecular Endocrinology

Background:

• Genetic selection in commercial broilers influences somatotropic gene expression.
• Developmental shifts in insulin-like growth factor (IGF) and IGF binding protein (IGFBP) expression are critical for rapid growth and muscle accretion.

Purpose of the Study:

• To investigate developmental changes in somatotropic axis activity from embryonic day 12 to post-hatch day 21 in broilers.
• To analyze gene expression of IGFs and IGFBPs in liver and breast muscle, and circulating IGF levels.

Main Methods:

• Gene expression analysis of IGFs and IGFBPs in broiler liver and pectoralis major muscle.
• Measurement of circulating IGF1 and IGF2 levels in post-hatch broilers.

Main Results:

• Liver IGF1 expression surged post-hatch, while muscle IGF1 showed dynamic changes throughout development.
• IGFBP expression varied significantly between embryogenesis and post-hatch, with specific patterns in liver and breast muscle.
• Circulating IGF1 and IGF2 levels remained stable from hatch to day 21, indicating localized regulation.

Conclusions:

• Post-hatch IGF action is primarily modulated by target tissue IGF receptor 1 (IGFR1) and IGFBP expression, not circulating hormone levels.
• Differential expression of IGFBPs in the liver and muscle suggests their role in regulating metabolic transition and muscle growth.
• Developmental gene expression patterns of IGFBPs provide a basis for understanding somatotropic signaling in broiler growth and muscle accretion.