Norman H D, Powell R L, Wright J R, Sattler C G
Animal Improvement Programs Laboratory, Agricultural Research Service, USDA, Beltsville, MD 20705-2350, USA.
J Dairy Sci. 2001 Aug;84(8):1899-912. doi: 10.3168/jds.S0022-0302(01)74631-0.
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 1990s was 11 for Ayrshires, 24 for Brown Swiss, 21 for Guernseys, 1261 for Holsteins, 112 for Jerseys, and 3 for Milking Shorthorns. Mean parent age at progeny-test (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 mo for sires, 47 mo for dams, and 136 mo for maternal grandsires during the mid 1990s. 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 1990s. Mean numbers of daughters and herds per PT bull generally declined except for Holsteins, which increased during the early 1990s 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.
研究了自1960年以来美国人工授精（AI）组织后裔测定（PT）计划的特征变化。20世纪90年代中期，主要AI组织每年进行后裔测定的公牛平均数量，爱尔夏牛为11头，瑞士褐牛为24头，娟姗牛为21头，荷斯坦牛为1261头，泽西牛为112头，乳用短角牛为3头。后裔测定（PT）公牛出生时的平均父系年龄除乳用短角牛外均有所下降；荷斯坦牛和泽西牛的后裔测定（PT）公牛出生时母系祖父的平均年龄下降，但其他品种有所上升。对于荷斯坦牛，20世纪90年代中期后裔测定（PT）公牛出生时，父系的平均祖先年龄为85个月，母系的为47个月，母系祖父的为136个月。到1999年，通过胚胎移植产生的后裔测定（PT）公牛的比例，瑞士褐牛增至78%，荷斯坦牛增至80%。后裔测定（PT）公牛的近亲繁殖随时间增加，20世纪90年代中期，瑞士褐牛为3.8%，泽西牛为6.4%（荷斯坦牛为5.6%）。除荷斯坦牛外，每头后裔测定（PT）公牛的平均女儿数量和牛群数量总体上有所下降，荷斯坦牛在20世纪90年代初增至61个女儿和44个牛群。后裔测定（PT）女儿所在州的平均数量增加；1994年，荷斯坦牛后裔测定（PT）公牛的女儿中，22%在加利福尼亚州，13%在威斯康星州，12%在纽约州，10%在宾夕法尼亚州和明尼苏达州。1998年，首次产犊母牛中后裔测定（PT）女儿的比例增加，乳用短角牛为6%，爱尔夏牛为22%（荷斯坦牛为14%）。后裔测定（PT）女儿的登记比例下降，荷斯坦牛为19%，其他品种约为80%。
