Early stages of embryonic development in two rabbit genotypes

Area of Science:

• Reproductive biology
• Animal science
• Embryology

Background:

• Early embryonic loss significantly impacts rabbit prolificacy.
• Understanding the causes of embryonic loss is crucial for improving reproductive efficiency in rabbit farming.

Purpose of the Study:

• To investigate the causes of early embryonic loss in Californian doe-rabbits within the first 4 days post coitum (p.c.).
• To compare embryonic development between Californian and New Zealand doe-rabbits.

Main Methods:

• Doe-rabbits (Californian and New Zealand) were studied at 24 and 60 hours post coitum (p.c.).
• Embryonic development was assessed by in toto examination at 24 h p.c. and by counting morula nuclei on histological sections at 60 h p.c.

Main Results:

• At 24 h p.c., 37% of Californian eggs had not divided, compared to a highly significant 5.3% in New Zealand eggs.
• At 60 h p.c., Californian embryos showed more variable development, though mean morula nuclei counts were not significantly different between breeds.
• A higher proportion of unfertilized or retarded-segmenting eggs was observed in Californian rabbits.

Conclusions:

• The primary cause of lower prolificacy in Californian rabbits is the higher incidence of unfertilized or developmentally delayed eggs compared to New Zealand rabbits.
• These findings highlight a significant genetic or physiological difference affecting early embryonic development between the two rabbit breeds.