|Wright, Janice - Jan|
Submitted to: American Dairy Science Association Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 7/24/2001
Publication Date: N/A
Citation: Interpretive Summary:
Technical Abstract: Progeny-test (PT) programs of US artificial-insemination (AI)units were examined to determine timeliness, PT daughter distribution, and future use of PT bulls. Means, standard deviations (SD), and deciles for bull age at semen distribution, PT daughter birth, and PT daughter calving were calculated by breed for bulls entering AI since 1959. Mean Holstein bull age at semen distribution (16 mo) changed little over time, but SD decreased from 4 mo in the 1960s to 2.4 mo in the 1990s. Most bulls (80%) had semen released by 18 mo. Mean Holstein bull age at PT daughter birth and calving declined by 4 mo from the 1960s to the 1990s to 29 mo and 56 mo; SD decreased from 6 to 3 mo. Usually for other breeds, bulls were older at PT daughter birth and calving, and SD were larger. Mean Holstein bull age when 80% of PT daughters had been born declined by 5 mo from the 1960s to the early 1990s; for other breeds, bulls were older (36 to 41 mo). Mean Holstein bull age when 80% of PT daughters had calved declined by 6 mo from the 1960s to the 1990s; for other breeds, bulls were older. Percentage of first-lactation Holstein cows that were PT daughters increased over time to 14%. For Holsteins, percentage of herds with >=5 first-lactation records that were usable for evaluation but with no usable PT records decreased from 85% in 1965 to 39% in 1998, whereas percentages increased from 11 to 38% for herds with from 1 to 19% PT records and from 1 to 5% for herds with >50% PT records. Percentage of Holstein PT bulls returned to AI declined from >50% for bulls with PT entry in 1965 to about 15% for bulls with PT entry around 1990; for other breeds, about 20% of recent bulls returned to service. Rapid sampling and increased selection intensity of PT programs have lead to more rapid genetic progress.