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Adjustment of breeding values for past and future inbreeding

Adjustment of breeding values for past and future inbreeding. Paul VanRaden *, Lori Smith Animal Improvement Programs Laboratory Agricultural Research Service, USDA Beltsville, Maryland. Selection and Mating. Selection Rank animals from best to worst Decide which animals reproduce

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Adjustment of breeding values for past and future inbreeding

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  1. Adjustment of breeding values for past and future inbreeding Paul VanRaden*, Lori Smith Animal Improvement Programs Laboratory Agricultural Research Service, USDA Beltsville, Maryland

  2. Selection and Mating • Selection • Rank animals from best to worst • Decide which animals reproduce • Mating • Predict the merit of pairs • Decide which animals are paired • Select/Mate • Do both steps at once • Better in theory but not practical

  3. Main effects and interactions • Transmitting ability • Mean value of progeny of random mates • Falconer • Nonadditive merit • Parents’ combined value minus parent average • Inbreeding depression • Best Transmitting Ability • Value of progeny of least related mates • Value of genes in later generations

  4. Past and future inbreeding • Past inbreeding adjusted yield = yield - (inbreeding) • Future inbreeding adjusted PTA = PTA +  (expected inbreeding) combined merit = PTAS + PTAD +  (inbreedingS,D) PTAS and PTAD are adjusted for past inbreeding • Mating programs

  5. Test of adjustments • Mate population • 600 females born in 1996 • Data file • All Holsteins evaluated August 1998 • Regressions • Previously estimated by Wiggans et al. (1995) • Timing • 4 hours for expected inbreeding; 0 for evaluation

  6. PTA Correlations Adjustments None Past Past, Future None 1.0000 .9974 .9976 Past .9974 1.0000 .9976 Past, Future .9976 .9976 1.0000 From 584 active AI bulls

  7. Value of adjustment • Current progress = $200 million/yr • Increased progress = 100/(1-.9976) = .24% • Yearly benefit = $.5 million/yr • Net present value = $10 million/yr

  8. Genetic Trend Cows born 1980-1990kg/year Published trend 104.4 Additive trend 107.4 Additive - inbreeding loss 98.2

  9. Interbull • Ideal • Each country adjusts for past inbreeding • Do across-country evaluation (MACE) • Add future inbreeding within country • Proposed • USA adjusts for past and future inbreeding • MACE accounts for change in trend • Alternative • Adjust only the Net Merit index

  10. Conclusions • Additive and nonadditive effects can be separated • PTAs may include expected nonadditive (expected inbreeding  0) • Trends change more than rank • Uniform policy best for Interbull

  11. Implementation • Adjustments easy for U.S. bulls. • Foreign pedigree may be missing. • Can’t add future inbreeding if foreign PTA includes past inbreeding • Adjust for past and future in September Interbull test run. • Hope MACE converts to new scale.

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