Estimation of accuracy and bias in genetic evaluations with genetic groups using sampling

Area of Science:

• Animal Breeding and Genetics
• Quantitative Genetics
• Statistical Genetics

Background:

• Accurate genetic evaluations are crucial for effective animal breeding programs.
• Estimating breeding values (EBVs) requires accounting for genetic group effects and their associated uncertainty.
• Existing methods may not fully capture the nuances of genetic group contributions to EBV accuracy and bias.

Purpose of the Study:

• To develop and apply a novel simulation-based method for calculating the accuracy and bias of estimated genetic group effects and EBVs.
• To quantify the accuracy and bias of genetic group effects and EBVs across multiple traits and genetic groups in a beef cattle dataset.
• To assess the impact of genetic group accuracy on the overall reliability of EBVs.

Main Methods:

• A simulation approach was employed, repeatedly generating phenotypes based on defined data and pedigree structures.
• Best Linear Unbiased Prediction (BLUP) with genetic groups incorporated into the relationship matrix was used for analysis.
• Accuracy was determined by the correlation between true and estimated values, while bias was measured by the difference across multiple simulation replicates.

Main Results:

• Small biases were detected for most genetic group effects and their comparisons, generally not significant relative to phenotypic standard deviation.
• The trait 'calf quality' exhibited larger biases due to limited performance records.
• Accuracy of genetic group effects varied widely, from 0.02 (feed intake) to >0.97 (carcass conformation), depending on data availability.
• Accuracies of EBVs within and across genetic groups differed, suggesting the need to consider genetic group accuracy in EBV reporting.

Conclusions:

• The developed simulation method provides a robust assessment of accuracy and bias in genetic evaluations, incorporating genetic group uncertainty.
• While biases are often minimal, the substantial variation in accuracy underscores the importance of genetic group information.
• Accuracies of EBVs can differ depending on whether they are considered within or across genetic groups, necessitating careful interpretation and reporting of genetic evaluations.