Effects of Selection Bias on Sire Evaluation Procedures

Open Access
Publisher Website
Google Scholar
Abstract
Problems associated with selected records in methods of sire evaluation were examined, and multiplicative factors for adjustment were developed to incorporate later lactation records in sire evaluation procedures where a 1st record is missing. All Holstein records in the Dairy Herd Improvement Association files at Beltsville, Maryland [USA], with freshening dates between 1960-1973 were used to quantify the amount of selection bias in later records that do not have 1st-lactation information available. Differences for lactation groupings show the amount of bias from selection in these records. The model included an overall mean, effects due to the herd-year-season of freshening, and opportunity groups that were formed depending on the number of later lactations for individual cows. These multiplicative factors can be used to adjust approximately 47% of cows in the files that do not have 1st-lactation information. These records can be incorporated, if needed to increase accuracy or increase comparisons, in the Best Linear Unbiased Prediction method or the Modified Contemporary Comparison method or sire evaluation.

This publication has 4 references indexed in Scilit: