POTENTIAL BIASES IN PREDICTED TRANSMITTING ABILITIES OF FEMALES FROM PREFERENTIAL TREATMENT

Data were simulated according to the USDA animal model to determine po tential biases in female PTA from preferential treatment. Ten scenario s for preferential treatment were investigated. Scenarios were defined according to three factors: number of records for the cows receiving preferential treatment, whether all or only second and later records r eceived preferential treatment, and whether preferential treatment was added only to records of cows selected for preferential treatment or to selected cows and their relatives (dam or dam and maternal sibs). T hree levels of preferential treatment were studied. Each was studied s eparately to allow straightforward determination of whether bias incre ased linearly as level of preferential treatment increased. For each s cenario, bias increased linearly as level of preferential treatment in creased, but magnitude of bias varied across scenarios. As a proportio n of preferential treatment effect, bias in PTA ranged from .06 to .39 . Affording preferential treatment to relatives increased bias more th an increasing the number of lactations with preferential treatment.