Alternatives for examining daughter performance of progeny-test bulls between official evaluations

摘要

In August 2007, the USDA changed from calculating official genetic evaluations quarterly to triannually in conjunction with the schedule change for international evaluations. To offset part of the delay in providing genetic information because of the reduced frequency of official evaluations, industry cooperators requested that interim evaluations be initiated for progeny-test (PT) bulls based on first-lactation records from PT daughters and their contemporaries that calved recently in cooperator herds. Alternatives for interim evaluations were studied to determine which would characterize genetic merit of PT bulls most accurately. Four alternative Holstein data sources were examined based on maximum data interval (most recent 12 or 18 mo of first calvings) and minimum number of PT daughters in herd (≥ 1 or ≥ 5). The highest correlation between August 2006 interim and official evaluations for milk yield was 0.980 for interim evaluations based on the most recent 18 mo of first calvings from cooperator herds with ≥ 1 PT daughter. That high correlation confirmed that interim evaluations based on limited data could provide genetic estimates of value between official evaluations. With the support of the Council on Dairy Cattle Breeding, the USDA initiated 3 interim evaluations each year with release limited to PT bulls with ≥ 10 daughters and an increase in reliability since the most recent official evaluation.