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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 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 • Mating • Predict the merit of pairs • Decide which animals are paired • Select/Mate • Do both steps at once • Better in theory but not practical
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
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
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
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
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
Genetic Trend Cows born 1980-1990kg/year Published trend 104.4 Additive trend 107.4 Additive - inbreeding loss 98.2
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
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
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.