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Genetic Evaluations for Mixed Breed Populations

Genetic Evaluations for Mixed Breed Populations. Goals. Evaluate crossbred animals without biasing purebred evaluations Accurately estimate breed differences Compute national evaluations and examine changes PTA’s of purebreds and crossbreds Changes in reliability

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Genetic Evaluations for Mixed Breed Populations

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  1. Genetic Evaluations for Mixed Breed Populations

  2. Goals • Evaluate crossbred animals without biasing purebred evaluations • Accurately estimate breed differences • Compute national evaluations and examine changes • PTA’s of purebreds and crossbreds • Changes in reliability • Display results without confusion

  3. Methods • All-breed animal model • Purebreds and crossbreds together • Unknown parents grouped by breed • Variance adjustments by breed • Age adjust to 36 months, not mature • 1988 software, good convergence • Within-breed-of-sire model examined but not used

  4. Unknown Parent Groups • Groups formed based on • Birth year (flexible) • Breed (must have >10,000 cows) • Path (dams of cows, sires of cows, parents of bulls) • Origin (domestic vs other countries) • Paths have >1000 in last 15 years • Groups each have >500 animals

  5. Data • Numbers of cows of all breeds • 22.6 million for milk and fat • 16.1 million for protein • 22.5 million for productive life • 19.9 million for daughter pregnancy rate • 10.5 million for somatic cell score • Type evaluated in separate breed files • Calving ease joint HO, BS, and HO x BS • Goats in all-breed model since 1988

  6. Crossbred Cowswith 1st parity records

  7. Recent Sires of Crossbred CowsSires born since 1997

  8. Reliability • Crossbred cows • Will have PTAs, most did not before • Accurate PTAs from both parents • Purebred animals • Information from crossbred relatives • More contemporaries

  9. All- vs Within-Breed EvaluationsCorrelations of PTA Milk

  10. Display of PTAs • Genetic base • Convert all-breed base back to within-breed-of-sire bases • Each animal gets just one PTA • PTAbrd = (PTAall – meanbrd) SDbrd/SDall • Heterosis and inbreeding • Both effects removed in the animal model • Heterosis added to crossbred animal PTA • Expected Future Inbreeding (EFI) and merit differ with mate breed

  11. Genetic Standard Deviation Ratios

  12. Schedule • Interbull test run Sept. 1, 2006 • Trend validation • Convert all-breed PTA back to within-breed bases • Scientific publication (JDS) • Implementation • Expected February 2007

  13. Conclusions • All breed model accounts for: • General heterosis • Unknown parent groups by breed • Heterogeneous variance by breed • PTA converted back to within breed bases, crossbreds to breed of sire • PTA changes more in breeds with fewer animals

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