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Experience with a test-day model.

L R Schaeffer1, J Jamrozik, G J Kistemaker

  • 1Centre for Genetic Improvement of Livestock, Department of Animal and Poultry Science, University of Guelph, ON, Canada. lrs@sherlock.aps.uoguelph.ca

Journal of Dairy Science
|May 23, 2000
PubMed
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The Canadian Test-Day Model uses 12 traits from early lactations to estimate breeding values for dairy cows. This new model shows high correlation with previous methods, improving genetic evaluations for milk production and health traits.

Area of Science:

  • Animal Breeding and Genetics
  • Dairy Science
  • Quantitative Genetics

Background:

  • Traditional genetic evaluation models often use complete lactation data.
  • The Canadian dairy industry sought to improve genetic evaluations using test-day records.

Purpose of the Study:

  • To introduce and evaluate the Canadian Test-Day Model (CTDM) for genetic evaluations in dairy cattle.
  • To compare the CTDM with the traditional 305-day lactation model.

Main Methods:

  • A 12-trait random regression animal model was developed using over 22 million test-day records from 1.4 million cows across seven breeds.
  • Random regressions utilized Wilmink's three-parameter function for genetic and permanent environmental effects.
  • Estimated breeding values (EBVs) were derived for milk, fat, protein yields, and somatic cell scores.

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Main Results:

  • The CTDM generated 36 additive genetic solutions per animal, combined into comprehensive EBVs.
  • High correlations were observed between CTDM yield EBVs and previous 305-day model EBVs (0.97 for bulls, 0.93 for cows).
  • Implementation necessitated novel methods for EBV reliability approximation and data handling.

Conclusions:

  • The CTDM provides a robust framework for genetic evaluation in dairy cattle, incorporating test-day data effectively.
  • The model's high correlation with existing methods suggests a smooth transition for the industry.
  • Further research is needed on combining lactation-specific EBVs and industry adoption strategies.