Development of bovine embryos derived from reproductive techniques

Area of Science:

• Reproductive Biology
• Developmental Biology
• Veterinary Science

Background:

• Assisted reproduction techniques (ART) have advanced bovine breeding.
• Significant embryonic and fetal mortality occurs during the first trimester of gestation in ART-derived pregnancies.
• Developmental pathways in ART may diverge from in vivo conditions.

Purpose of the Study:

• To investigate and compare embryonic and fetal membrane development in bovine following fixed-time AI (FTAI), in vitro fertilization (IVF), and nuclear transfer (NT).
• To identify specific developmental anomalies associated with different ART methods, particularly nuclear transfer.

Main Methods:

• Comparative morphological and developmental analysis of bovine embryos and fetal membranes.
• Assessment of yolk-sac development, chorioallantoic membrane vascularization, and overall embryonic growth rates.
• Evaluation of conceptus size, liver positioning, and cardiac morphology in cloned embryos.

Main Results:

• Nuclear transfer (NT) embryos exhibited abnormal yolk-sac development onset.
• Yolk-sac morphology and positioning relative to the amniotic membrane differed from in vivo conditions across all ART groups.
• Vascularization of the chorioallantoic membrane was delayed and reduced in NT gestations.
• NT conceptuses were smaller, with some showing ectopic liver positioning and cardiac abnormalities.

Conclusions:

• The yolk-sac and cardiovascular system are susceptible to morphogenetic alterations in bovine ART.
• Developmental anomalies identified in NT pregnancies may contribute to high intrauterine mortality.
• Future research should focus on gene expression and early vascularization to elucidate the causes of ART-related pregnancy loss.