BIASES IN PREDICTED TRANSMITTING ABILITIES OF SIRES WHEN DAUGHTERS RECEIVE PREFERENTIAL TREATMENT

Data were simulated according to the USDA animal model to determine bi ases in sire PTA when daughters receive preferential treatment. Two sc enarios were investigated. For scenario 1, all daughters were randomly distributed across herds. Bias increased with total number of daughte rs but at a decreasing rate. For a given total number of daughters, bi as increased linearly as the percentage of daughters receiving prefere ntial treatment increased from 25 to 100%. Expressed as a proportion o f 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 preferentia l treatment were randomly distributed across 378 other herds. Total nu mber of daughters was 20, 30, or 40, and the percentage of daughters r eceiving preferential treatment was 50, 75, or 100% in scenario 2. Two sets of herd sizes were used. With the smaller herds, bias was zero w hen all daughters received preferential treatment; otherwise, bias ran ged from .08 to .10. With the larger herds, biases increased as the pe rcentage of daughters receiving preferential treatment increased. The range in bias was .10 to .18 for scenario 2 for the larger herds.