|Sattler, C - NAAB|
Submitted to: Journal of Dairy Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: April 13, 2001
Publication Date: N/A
Interpretive Summary: Attaining a high rate of genetic improvement for dairy cattle often depends on successful operation of a progeny-test (PT) program for bulls. Statistics on scope and characteristics of PT programs were updated for AI organizations in the United States over the last 40 years. For major organizations, numbers of PT bulls increased through the mid-1990's and then began to decline slightly. Average parent age at bull birth decreased for all breeds except Milking Shorthorn; average age of maternal grandsire at bull birth decreased for Holsteins and Jerseys but increased for other breeds. Percentage of PT bulls from embryo transfer increased steadily for Guernseys, Brown Swiss, Holsteins, and Jerseys. The dairy industry reduced generation interval for PT daughters by selecting younger parents of PT bulls and using new reproductive technologies. Percentage of PT daughters that were registered declined and was 19% for Holsteins and around 80% for other breeds. Inbreeding in PT bulls increased for all breeds and ranged from 3.8% for Brown Swiss to 6.4% for Jerseys for recent PT bulls, which is slightly higher than inbreeding in the milk-recorded population. Average numbers of PT daughters and herds per bull generally declined for all breeds except for slight increases for recent Ayrshire and Holstein PT bulls. Percentage of 1st-lactation cows that were PT daughters increased and ranged from 6% for Milking Shorthorns to 22% for Ayrshires (14% for Holsteins) during 1998; further increases are expected as the U.S. dairy population declines. Average number of states with PT daughters increased, which aids in reducing environmental distortions in genetic evaluations. Review of updated statistics by AI organizations should assist in improving operational efficiency and anticipating and preventing problems.
Technical Abstract: Characteristics of progeny-test (PT) programs of artificial-insemination (AI) organizations in the United States were examined for changes since 1960. Mean number of bulls that were progeny tested annually by major AI organizations during the mid-1990's was 11 for Ayrshires, 24 for Brown Swiss, 21 for Guernseys, 1,261 for Holsteins, 112 for Jerseys, and 3 for Milking Shorthorns. Mean parent age at PT bull birth decreased except for Milking Shorthorns; mean age of maternal grandsire at bull birth decreased for Holsteins and Jerseys but increased for other breeds. For Holsteins, mean ancestor ages at PT bull birth were 85 months for sires, 47 months for dams, and 136 months for maternal grandsires during the mid-1990's. Percentage of PT bulls that resulted from embryo transfer increased to 78% for Brown Swiss and 80% for Holsteins by 1999. Inbreeding in PT bulls increased over time and ranged from 3.8% for Brown Swiss to 6.4% for Jerseys (5.6% for Holsteins) during the mid-1990's. Mean numbers of daughters and herds per PT bull generally declined except that Holsteins increased during the early 1990's to 61 daughters and 44 herds. Mean number of states in which PT daughters are located increased; for Holstein PT bulls during 1994, 22% of daughters were in California, 13% in Wisconsin, 12% in New York, and 10% in Pennsylvania and Minnesota. Percentage of first-lactation cows that were PT daughters increased and ranged from 6% for Milking Shorthorns to 22% for Ayrshires (14% for Holsteins) during 1998. Percentage of PT daughters that were registered declined and was 19% for Holsteins and around 80% for other breeds.