Use of Haplotypes to Predict Selection Limits and Mendelian Sampling

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Presentation from the 2010 ADSA meeting on the use of genomic information to calculate selection limits and Mendelian sampling.

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Use of Haplotypes to Predict Selection Limits and Mendelian Sampling

  1. 1. J. B. ColeJ. B. Cole** and P. M. VanRadenand P. M. VanRaden Animal Improvement Programs Laboratory Agricultural Research Service, USDA Beltsville, MD 20705-2350 john.cole@ars.usda.gov Use of Haplotypes to Predict Selection Limits and Mendelian Sampling
  2. 2. ADSA, July 2010 (2) Cole and VanRaden Introduction • Mendelian sampling is the difference between an individual's PTA and its PA • Sustained genetic gain under selection depends on Mendelian sampling variance (Woolliams et al., 1999) • Increased reliabilities from genomic selection due to better estimates of Mendelian sampling (Hayes et al., 2009)
  3. 3. ADSA, July 2010 (3) Cole and VanRaden Introduction (cont’d) • You do not benefit substantially from genomic selection until you have a large enough pool of genotyped animals to provide good estimates of marker effects • Good marker effects are essential for reliable prediction of Mendelian sampling
  4. 4. ADSA, July 2010 (4) Cole and VanRaden Objectives • Describe the predicted Mendelian sampling (MS) variation in Brown Swiss, Holstein, and Jersey cattle • Calculate selection limits based on haplotypes present in the genotyped population • Examine adjustments to breeding values for changes in heterozygosity
  5. 5. ADSA, July 2010 (5) Cole and VanRaden Materials • 43,382 SNP from the Illumina BovineSNP50 • SNP solutions from the June, 2010 evaluation • Three breeds • 1,455 Brown Swiss males and females • 40,351 Holstein males and females • 4,064 Jersey males and females • Three traits • Daughter pregnancy rate (DPR) • Milk yield (Milk) • Lifetime net merit (NM$)
  6. 6. ADSA, July 2010 (6) Cole and VanRaden Methods • Haplotypes imputed with findhap.f90 (VanRaden et al., 2010) • Calculations and simulations performed with SAS 9.2 • Plots produced with R 2.10.1 and ggplot2 0.8.7 (Wickham, 2009) • Operating system is 64-bit RedHat Enterprise Linux 5
  7. 7. ADSA, July 2010 (7) Cole and VanRaden Predicted Mendelian sampling • Lower bound assumes all SNP on a chromosome are unlinked • Upper bound assumes all SNP on a chromosome are perfectly linked • “I have discovered a truly marvelous proof…this slide is too narrow to contain it” • Also could be calculated from linkage disequilibrium blocks
  8. 8. ADSA, July 2010 (8) Cole and VanRaden Distribution of Mendelian sampling variance
  9. 9. ADSA, July 2010 (9) Cole and VanRaden Predicted Mendelian sampling variance Trait Breed Lower Expected Upper DPR BS 0.09 1.45 1.57 HO 0.57 1.45 4.02 JE 0.09 0.98 1.27 Milk BS 35,335 215,168 507,076 HO 228,011 261,364 1,069,741 JE 150,076 205,440 601,979 NM$ BS 2,539 19,602 40,458 HO 16,601 19,602 87,449 JE 3,978 19,602 44,552
  10. 10. ADSA, July 2010 (10) Cole and VanRaden Why are Holsteins so different? • There are many more HO haplotypes represented • There are multiple QTL affecting NM$ in HO
  11. 11. ADSA, July 2010 (11) Cole and VanRaden Sampling variance over time — DPR BS HO JE
  12. 12. ADSA, July 2010 (12) Cole and VanRaden Sampling variance over time — Milk BS HO JE
  13. 13. ADSA, July 2010 (13) Cole and VanRaden Sampling variance over time — NM$ BS HO JE
  14. 14. ADSA, July 2010 (14) Cole and VanRaden Correlations with inbreeding Lower Upper Trait Breed Genomic Pedigree Genomic Pedigree DPR BS -0.73 -0.38 -0.02 0.09 HO -0.77 -0.40 -0.11 -0.03 JE -0.83 -0.53 -0.01 0.06 Milk BS -0.86 -0.55 -0.05 0.03 HO -0.12 -0.05 -0.10 -0.03 JE -0.01 0.03 -0.04 0.04 NM$ BS -0.85 -0.49 0.03 0.13 HO -0.21 -0.12 -0.11 -0.03 JE -0.86 -0.53 -0.11 -0.02
  15. 15. ADSA, July 2010 (15) Cole and VanRaden Selection limits • Lower bound found by summing the best chromosomes • Upper bound found by summing the best alleles at each locus • NM$ was adjusted to account for changes in heterozygosity
  16. 16. ADSA, July 2010 (16) Cole and VanRaden Calculated selection limits Trait Breed Lower Upper Largest DGV DPR BS 20 53 8 HO 40 139 8 JE 19 53 5 Milk BS 14,193 34,023 4,544 HO 24,883 77,923 7,996 JE 16,133 40,249 5,620 NM$ BS 3,857 9,140 1,102 HO 7,515 23,588 2,528 JE 4,678 11,517 1,556
  17. 17. ADSA, July 2010 (17) Cole and VanRaden Adjusting for heterozygosity • Chromosomal EBV for NM$ were adjusted by adding or subtracting 6% of an additive genetic standard deviation ($11.88) per 1% change in heterozygosity (Smith et al., 1998) • Only 4 chromosomes (BTA 6, 10, 14, and 16) differed between the adjusted and unadjusted groups
  18. 18. ADSA, July 2010 (18) Cole and VanRaden What’s the best cow we can make? A “Supercow” constructed from the best haplotypes in the Holstein population would have an EBV(NM$) of $7515
  19. 19. ADSA, July 2010 (19) Cole and VanRaden Conclusions • Selection limits and sampling variances differ among breeds • Sampling variance has decreased slightly over time • The top animals in each breed are well below predicted selection limits • Adjustment for heterozygosity had little effect on breeding values for NM$
  20. 20. ADSA, July 2010 (20) Cole and VanRaden Questions?

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