Author
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Vanraden, Paul |
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Powell, Rex |
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Submitted to: Interbull Annual Meeting Proceedings
Publication Type: Proceedings Publication Acceptance Date: 5/26/2002 Publication Date: N/A Citation: N/A Interpretive Summary: Longevity is an indicator of overall health of the cow and overall satisfaction of the owner, but the trait is defined and analyzed differently among countries. Some simple changes in the measure of daughter contribution and heritability could improve accuracy of proposed international evaluations for longevity. Longevity evaluations from 11 countries (Canada, Denmark, France, Germany, Israel, Italy, New Zealand, Sweden, Switzerland, The Netherlands, and the United States) were examined, and relationships with other traits on each country's scale were documented. Relationships of longevity with somatic cell score (mastitis resistance) and with conformation traits were fairly uniform across countries. Relationships of longevity with yield traits varied. More uniform trait and parameter definitions could increase relationships among and value of potential international longevity evaluations. Improved definitions of daughter contribution and heritability were suggested for different types of statistical analysis currently in use. A goal is that national and international reliability (accuracy) reflect true reliability for all evaluations. Further research on national and international evaluations should have high priority because most national economic indexes assign high value to longevity. Technical Abstract: Longevity is an indicator of overall health of the cow and overall satisfaction of the owner, but the trait is defined and analyzed differently among countries. Longevity evaluations from 11 countries (Canada, Denmark, France, Germany, Israel, Italy, New Zealand, Sweden, Switzerland, The Netherlands, and the United States) were examined, and correlations with other traits on each country's scale were obtained. Correlations of longevity with somatic cell score and conformation traits were fairly uniform across countries. Correlations with yield traits varied for countries that reported functional longevity and for those that reported true longevity. Some correlations of yield with functional longevity were higher than correlations of yield with true longevity. More uniform trait and parameter definitions could increase correlations among and value of potential international longevity evaluations. Improved definitions of effective daughter contribution and heritability were suggested for different types of statistical analysis currently in use. Estimates of genetic correlations and standard deviations may be sensitive to incorrect values because fewer bulls have evaluations with high reliability. A goal is that national and international reliability reflect true reliability for all evaluations. Further research on national and international evaluations should have high priority because most national indexes assign high economic value to longevity. |
