Profiles of mRNA expression of related genes in the duck hypothalamus–pituitary growth axis during embryonic and early post-hatch development

• The ontogeny of early growth of two different duck breeds was compared.
• The pattern of HPGA-related genes mRNA expression of two duck breeds was compared.
• Breed specificity in duck early growth was correlated with HPGA genes expression.
• Species variance was found regarding HPGA-related gene expression of bird embryo.
• Hepatic IGF-1 may be involved in mediating a genetic effect on ducks early growth.

In this study, the ontogeny of body and liver weight and the pattern of related gene mRNA expression in the hypothalamus–pituitary growth axis (HPGA) of two different duck breeds (Anas platyrhynchos domestica) were compared during embryonic and post-hatch development. Duck hypothalamic growth hormone release hormone (GHRH), somatostatin (SS), pituitary growth hormone (GH), liver growth hormone receptor (GHR) and insulin-like growth factor-I (IGF-1) mRNA were first detected on the 13th embryonic day. During early duck development, SS maintained a lower expression status, whereas the other four genes exhibited highly significant variations in an age-specific manner. Highly significant breed specificity was observed with respect to hepatic IGF-1 mRNA expression, which showed a significant breed–age interaction effect. Compared with previous studies on chickens, significant species differences were observed regarding the mRNA expression of bird embryonic HPGA-related genes. During early development, highly significant breed and age specificity were observed with respect to developmental changes in body and liver weight, and varying degrees of significant linear correlation were found between these performances and the mRNA expression of HPGA-related genes in the duck HPGA. These results suggest that different genetic backgrounds may lead to differences in duck growth and HPGA-related gene mRNA expression, and the differential mRNA expression of related genes in the duck HPGA may be particularly important in the early growth of ducks. Furthermore, hepatic IGF-1 mRNA expression presented highly significant breed specificity, and evidence suggests the involvement of hepatic IGF-1 in mediating genetic effects on embryo and offspring growth in ducks.