Bovine embryo culture in vitro: new developments and post-transfer consequences

Area of Science:

• Reproductive biology
• Developmental biology
• Animal science

Background:

• Cattle blastocyst production has shifted from co-culture to sequential media systems, improving performance.
• Wholly defined, protein-free systems compromise cattle blastocyst metabolic function.
• Metabolic inhibitors and low oxygen are novel strategies for in vitro embryo development.

Purpose of the Study:

• To evaluate the impact of metabolic inhibitors and low oxygen on cattle blastocyst development in vitro.
• To investigate the causes of post-implantation fetal loss and fetal oversize in cattle embryo culture.
• To identify potential mechanisms linking allantoic development failure to fetal oversize.

Main Methods:

• In vitro culture of cattle embryos using sequential media.
• Application of metabolic inhibitors (NaN3, 2,4-dinitrophenol) and low oxygen (2%) during the peri-compaction period.
• Analysis of blastocyst yield and quality.
• Examination of fetal development and conceptus viability up to day 110, focusing on allantoic development.

Main Results:

• Metabolic inhibitors and low oxygen significantly increased blastocyst yield (10-20%) and quality.
• Despite improvements, cattle embryo culture is associated with fetal oversize and significant post-day 35 fetal loss.
• Fetal loss is linked to impaired allantoic development, potentially due to poor nutrient supply and waste removal.

Conclusions:

• Sequential media and specific in vitro treatments can enhance cattle blastocyst production.
• Significant challenges remain, including metabolic compromise in protein-free systems and post-implantation fetal loss.
• Disrupted allantoic development is a key factor in fetal loss and may be related to fetal oversize syndrome.