Biases in Predicted Transmitting Abilities of Sires When Daughters Receive Preferential Treatment

¹ Department of Animal Science, Iowa State University, Ames 50011

Data were simulated according to the USDA animal model to determine biases in sire PTA when daughters receive preferential treatment. Two scenarios were investigated.

For scenario 1, all daughters were randomly distributed across herds. Bias increased with total number of daughters but at a decreasing rate. For a given total number of daughters, bias increased linearly as the percentage of daughters receiving preferential treatment increased from 25 to 100%. Expressed as a proportion of the preferential treatment effect, bias ranged from .10 to .77.

For scenario 2, daughters receiving preferential treatment were placed in a single herd and remaining daughters that did not receive preferential treatment were randomly distributed across 378 other herds. Total number of daughters was 20, 30, or 40, and the percentage of daughters receiving preferential treatment was 50, 75, or 100% in scenario 2. Two sets of herd sizes were used. With the smaller herds, bias was zero when all daughters received preferential treatment; otherwise, bias ranged from .08 to .10. With the larger herds, biases increased as the percentage of daughters receiving preferential treatment increased. The range in bias was .10 to .18 for scenario 2 for the larger herds.

Key Words: predicted transmitting ability • preferential treatment • bias • daughters

Submitted on February 10, 1995
Accepted on May 1, 1995