Changes in Predicted Difference Milk with Increased Repeatability

Open Access
Publisher Website
Google Scholar
Abstract
All sire evaluations for 3733 Holstein bulls initially sampled through artificial insemination were studied for changes in predicted difference [PD] milk as evaluations increased in repeatability. Individual bulls contributed from 2-15 pairs of earlier and later evaluations. Average change in PD milk was 5 kg. Change in PD was correlated positively with change in records per daughter. PD increased by 5 kg of milk for each 0.1 increase in numbers of records per daughter. PD tended to increase with later records of daughters but to decrease when added records were for new daughters. PD tended to increase as repeatability increased to 70-79% and then to decrease as repeatability continued to increase. Minor misevaluation may be from genetic bases for 1st and later lactations not being comparable. Average absolute changes in PD were larger for larger changes in repeatability. Variability of pairs of sire proofs generally agreed with changes expected from a part-whole formula.