Comparison of gonadal hormone levels in turkey embryos incubated in long-term shell-less culture and in ovo

Department of Animal and Avian Sciences, University of Maryland, College Park 20742, USA.

Changes in concentrations of 17beta-estradiol (E2) and androgenic hormones were measured in turkey embryos incubated in long-term, shell-less culture (ex ovo) and in ovo. Blood samples were obtained from both sets of embryos on Days 14, 16, 18, 20, and 22 and from embryos incubated in ovo on Days 24, 26, and 28. Ex ovo and in ovo embryos showed no differences in either hormone within sexes, with one exception. On Day 14 of incubation, the ex ovo females had higher (P < 0.05) E2 levels (55.6+/-5.1 pg/mL) than the in ovo females (32.2+/-2.3 pg/mL); however, this result might have been due to the small sample size (n = 3) for ex ovo females. No significant differences were found in androgen concentrations between sexes in ovo on Days 24, 26, and 28 of incubation. However, on Days 24, 26, and 28, in ovo females showed highly significant differences (P < 0.01) in E2 compared with males of the same age. These results indicate a similar developmental pattern for the endocrine system in ovo and ex ovo through Day 22 of incubation. Further, there were sex differences in E2 that are likely to be critical for sexual differentiation that emerges late in embryonic development.