Author
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Powell, Rex |
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Vanraden, Paul |
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Submitted to: Interbull Annual Meeting Proceedings
Publication Type: Proceedings Publication Acceptance Date: 3/2/2003 Publication Date: N/A Citation: N/A Interpretive Summary: Profitable dairy cows not only produce large amount of high quality milk, but they are also durable enough to last for multiple lactations. Research in The Netherlands combined national longevity evaluations from 14 countries in a pilot study. Some countries evaluate how long cows live (true longevity) while others purport to measure longevity after adjustment for production (functional longevity). This study summarized the correlations of longevity with yield, udder health, and some type traits, within contributing countries, and across time. Analysis showed that some countries that intend to adjust for yield actually have a higher correlation between longevity and yield genetic evaluations than some countries that do not adjust for yield. Ideally, an effective adjustment would result in unrelated functional longevity and yield evaluations. Estimated genetic progress was higher for some countries than seemed reasonable based on either the expected relationship between longevity and other traits or the short time longevity evaluations had been available for selection. Relationships between longevity and measures of conformation and udder health were fairly uniform across countries. Correlations between the US productive life for foreign bulls and the pilot results were high enough to be quite comforting except for New Zealand where the seasonal grazing, demands for prompt conception, and emphasis on small cow size create an unusual situation. Importance of the various traits in influencing longevity varies across time and across countries at the same time. Although there are some questions that remain, the relationships among longevity measures are high enough that combination of data across countries is justified. That would provide longevity results on a country¿s scale for all the bulls in participating countries. Technical Abstract: A pilot run using multiple-trait, across-country evaluation methodology was applied by Dutch researchers to dairy cow longevity data from 14 countries. Those bull evaluations were studied for genetic trend, relationships with other traits, and consistency with purported longevity definitions. The US and 3 other participating countries evaluate how long cows live (true longevity) while the others measure longevity after adjustment for production (functional longevity). Some countries that reported that they adjust for yield actually had a higher correlation between longevity and yield genetic evaluations than do some countries that do not adjust for yield. A perfect adjustment would result in correlations of zero between functional longevity and yield evaluations. Genetic progress (measured as the correlation between longevity bull evaluations and birth year) was higher for some countries than seemed reasonable based on the relation to other traits and the time longevity evaluations have been available for selection. Relationships between longevity and measures of conformation and udder health were fairly uniform across countries. Correlations between the US productive life for foreign bulls and the pilot results were high enough to be encouraging except for New Zealand where the seasonal grazing, demands for prompt conception, and emphasis on small cow size create an unusual situation. Importance of the various traits in influencing longevity varies across time and across countries at the same time. Relationships among longevity measures from the different countries are high enough that combination of data across countries is justified, thus providing longevity results on a country¿s scale for all the bulls in participating countries. |
