In ovo corticosterone exposure does not influence yolk steroid hormone relative abundance or skeletal muscle development in the embryonic chicken

In ovo corticosterone (CORT) exposure reportedly reduces growth and alters body composition traits in meat-type chickens. However, the mechanisms governing alterations in growth and body composition remain unclear but could involve myogenic stem cell com-mitment, and/or the presence of yolk steroid hormones. This study investigated whether in ovo CORT exposure influenced yolk steroid hormone content, as well as embryonic myogenic development in meat-type chickens. Fertile eggs were randomly divided at embryonic day (ED) 11 and administered either a control (CON; 100 mu L of 10 mM PBS) or CORT solution (100 mu L of 10 mM PBS containing 1 mu g CORT) into the chorioallantoic membrane. Yolk samples were collected at ED 0 and ED 5. At ED 15 and hatch, embryos were humanely killed, and yolk and breast muscle (BM) samples were collected. The relative abundance of 15 steroid hormones, along with total lipid content was measured in yolk samples col-lected at ED 0, ED 5, ED 15, and ED 21. Muscle fiber number, cross-sectional area, and fascicle area occupied by muscle fibers were measured in BM samples collected at hatch. Relative expression of MyoD, MyoG, Pax7, PPARy, and CEBP/fi, and the sex steroid receptors were measured in BM samples collected at hatch. The adminis-tration of CORT had a limited effect on yolk steroid hor-mones. In ovo CORT significantly reduced fascicle area occupied by muscle fibers and CEBP/fi expression was increased in CORT exposed birds at hatch. In addition, the quantity of yolk lipid was significantly reduced in CORT-treated birds. In conclusion, in ovo exposure to CORT does not appear to influence early muscle develop-ment through yolk steroid hormones in embryonic meat-type chickens however, the results provide a comprehen-sive analysis of the composition of yolk steroid hormones in ovo at different developmental time points. The find-ings may suggest increased mesenchymal stem cell com-mitment to the adipogenic lineage during differentiation and requires further investigation.

Automated summary

In ovo corticosterone (CORT) exposure does not appear to influence early muscle development through yolk steroid hormones in embryonic meat-type chickens. However, this study provides a comprehensive analysis of the composition of yolk steroid hormones at different developmental time points. The findings suggest the possibility of increased mesenchymal stem cell commitment to the adipogenic lineage during differentiation and warrant further investigation.