The Effect of Commercial Genetic Selection on Somatotropic Gene Expression in Broilers: A Potential Role for Insulin-Like Growth Factor Binding Proteins in Regulating Broiler Growth and Body Composition

Abstract

The somatotropic axis influences growth and metabolism, and many of its effects are a result of insulin-like growth factor (IGF) signaling modulated by IGF-binding proteins (IGFBPs). Modern commercial meat-type (broiler) chickens exhibit rapid and efficient growth and muscle accretion resulting from decades of commercial genetic selection, and it is not known how alterations in the IGF system has contributed to these improvements. To determine the effect of commercial genetic selection on somatotropic axis activity, two experiments were conducted comparing legacy Athens Canadian Random Bred and modern Ross 308 male broiler lines, one between embryonic days 10 and 18 and the second between post-hatch days 10 and 40. Gene expression was evaluated in liver and breast muscle (pectoralis major) and circulating hormone concentrations were measured post-hatch. During embryogenesis, no differences in IGF expression were found that corresponded with difference in body weight between the lines beginning on embryonic day 14. While hepatic IGF expression and circulating IGF did not differ between the lines post-hatch, expression of both IGF1 and IGF2 mRNA was greater in breast muscle of modern broilers. Differential expression of select IGFBPs suggests their action is dependent on developmental stage and site of production. Hepatic IGFBP1 appears to promote embryonic growth but inhibit post-hatch growth at select ages. Results suggest that local IGFBP4 may prevent breast muscle growth during embryogenesis but promote it after hatch. Post-hatch, IGFBP2 produced in liver appears to inhibit body growth, but IGFBP2 produced locally in breast muscle facilitates development of this tissue. The opposite appears true for IGFBP3, which seems to promote overall body growth when produced in liver and restrict breast muscle growth when produced locally. Results presented here suggest that paracrine IGF signaling in breast muscle may contribute to overall growth and muscle accretion in chickens, and that this activity is regulated in developmentally distinct and tissue-specific contexts through combinatorial action of IGFBPs.

Dietary bile acids improve breast muscle growth in chickens through FXR/IGF2 pathway

“…To further explore the impact of BA on breast muscle development, a comprehensive analysis of gene expression levels revealed a significant upregulation of IGF2, IGFBP7, mTOR, MYH1B , and PAX7 . Previous research emphasizes the pivotal roles played by these genes, including IGF2 ( Florini et al, 1991 ), IGFBP7 ( Vaccaro et al, 2022 ), mTOR ( Erbay et al, 2003 ), MYH1B ( Weng et al, 2021 ), and PAX7 ( Kim et al, 2021 ), in influencing skeletal muscle development.…”

Breast muscle white striping and serum corticosterone reduced in broilers exposed to laser environmental enrichment

“…Decreased expression of MSTN is believed to be a result of genetic selection for fast growth rate and large breast muscle size, and the upregulated MSTN observed in laser-enriched breast tissue in conjunction with reduced WS and WB may therefore be an unexpected, positive outcome indicating altered, potentially more healthy regulatory mechanisms in breast muscle growth. The concurrent upregulation of IGF2 expression may support this hypothesis, as IGF2 has been shown to be increased in fast-growing broiler breast muscle previously ( Zhang et al, 2019 ) linking it with positive, posthatch muscle growth as well as embryonic muscle development ( Vaccaro et al, 2022 ).…”

Effects of Amino Acid Supplementation to a Low-Protein Diet on the Growth Performance and Protein Metabolism-related Factors in Broiler Chicks

“…Insulin-like growth factor binding proteins (IGFBPs) are produced in the liver and skeletal muscles[ 22 , 23 ]. Hepatic IGFBPs are released in the bloodstream and function as carrier proteins of serum IGF-1 in mammals and chickens[ 23 , 24 ].…”

“…Although the effect of dietary protein levels on IGFBP mRNA levels in skeletal muscle has not been investigated in chickens, mRNA levels of IGFBP-2 in breast muscle are increased by dietary leucine supplementation above recommended levels in 10-day-old broiler chicks[ 28 ]. In broiler chicks with high muscularity, IGFBP-2 mRNA levels are high in the PM[ 22 ]. Therefore, IGFBPs expressed in liver and skeletal muscles may be involved in the effects of AA supplementation on the growth performance of LP diet-fed broiler chickens.…”