Statistical models predicting embryo survival to term in cattle after embryo transfer

Area of Science:

• Reproductive biology
• Animal science
• Veterinary medicine

Background:

• Embryo survival rates to term in recipient cattle exhibit significant variability.
• Current models often assume embryo independence, which may not accurately reflect biological realities.
• Understanding factors influencing embryo survival is critical for improving cattle breeding efficiency.

Purpose of the Study:

• To evaluate whether a binomial independence model or a new model incorporating embryo (e) and recipient (r) factors adequately explains observed embryo survival rates in cattle.
• To analyze published calving data to assess the fit of different models.
• To identify key contributors to variation in embryo survival and calving success.

Main Methods:

• Systematic review and meta-analysis of 32 published papers, encompassing 47 datasets and 4560 recipient cattle.
• Calculation of observed embryo survival rate to term (p) for each dataset.
• Comparison of expected outcomes under a binomial distribution versus a maximum-likelihood estimated 'e and r' model.

Main Results:

• The model of embryo independence was rejected in 85% of the analyzed datasets.
• The proposed 'e and r' model adequately described the published data for recipients of single or twin embryos.
• Variation in embryo survival among laboratories was attributed to recipient competence, not embryo competence.

Conclusions:

• Embryo survival to term in cattle is not independent and is significantly influenced by recipient factors.
• The 'e and r' model provides a more accurate framework for understanding and comparing embryo and recipient contributions to calving success.
• Focusing on recipient competence is essential for improving overall embryo survival rates in cattle.