Relationships Between Characteristics of Herd of Bull-Dams and Predicting Transmitting Ability of Young Bulls

Abstract

Young bulls selected from Michigan herds for sampling by Select Sires Incorporated from 1975 to 1982 were identified. Data for herds from which young bulls were selected for year of young bull''s birth were acquired from the Michigan DHIA. Herd average milk production, intraherd standard deviation for milk production, coefficient of variation for milk production, average sire transmitting ability of cows in the herd, and intraherd standard deviation of sire transmitting ability were computed for each herd. These herd characteristics were used in prediction of young bull transmitting ability. When considered along with a pedigree index predictor, intraherd standard deviation for milk production was significant in prediction of young bull transmitting ability, but other herd characteristics were not. Young bulls were grouped by the intraherd milk variance of the herd from which they were selected. Evaluations based on progeny tests showed young bulls selected from herds with low intraherd milk variance were genetically superior to those selected from herds with high intraherd milk variance. Predicted transmitting abilities for young bulls selected from low variance herds were less biased, but predicted transmitting abilities for those selected from high variance herds were inflated. However, the variance of biasedness was slightly lower in variance herds.