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Selection for Fertility in Dairy Cattle

Selection for Fertility in Dairy Cattle. Factors Affecting Fertility. Environment and management Season, region, herd, age, milk yield Estrus detection and / or synchronization Voluntary waiting period Fertility of bull (ERCR in USA) Genes of cow (Dau. Pregnancy Rate)

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Selection for Fertility in Dairy Cattle

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  1. Selection for Fertility in Dairy Cattle

  2. Factors Affecting Fertility • Environment and management • Season, region, herd, age, milk yield • Estrus detection and / or synchronization • Voluntary waiting period • Fertility of bull (ERCR in USA) • Genes of cow (Dau. Pregnancy Rate) • Interaction of bull’s and cow’s genes • Inbreeding, recessives (CVM, DUMPS)

  3. Fertility Does Not Show Paul VanRaden, 1974

  4. For Fertility, You Need Data Paul VanRaden, 1995

  5. Problem: Cows Are Less FertileUSA Holsteins 1965-2000 Lactation 5th 4th 3rd 2nd 1st

  6. Coefficients of Variation (CV)Standard deviation divided by mean

  7. Pregnancy Rate • The percentage of nonpregnant cows that become pregnant during each 21-day time period • Pregnancy rate < conception rate • Cows that are not cycling • Estrus not expressed or detected • Typical pregnancy rates • 20% if calving interval is 14.3 months • 25% if calving interval is 13.6 months

  8. Pregnancy Rate and Days Open 100 90 80 70 60 Pregnancy Rate 50 40 30 20 10 1 2 3 4 5 6 7 8 9 0 60 81 102 123 144 165 186 207 228 249 Number of Chances Days Open

  9. Sources of Fertility Data Percentages from 1998-1999 records

  10. Distribution of Days OpenHolstein Calvings 1990 - 2001 Cows culled for reproductive reasons ≤ 50 ≥ 250

  11. Seasonal Effects on FertilityHolsteins calving since 1997 in each USA region

  12. USA Fertility Evaluation • Holstein data in evaluation • 44 million lactation records since 1960 • 17 million cows • Lactations 1-5 are included • Reliability for recently proven bulls • 59% REL for Daughter Pregnancy Rate • 61% REL for Productive Life • 69% REL for Somatic Cell Score • 85% REL for Milk Yield

  13. USA Evaluation Methods • Animal model, introduced Feb 2003 • Same programs as yield, PL, SCS • Compare cows within herd, season, and age • Convert days open to pregnancy rate = (233 – DO) / 4 • Parameter estimates used: • Heritability = 4% • Repeatability = 11% • Sire-by-herd interaction = 4%

  14. Recent USA ChangesNovember 2003 and November 2004 • Earlier evaluation of cow fertility • Records in progress used at 130 instead of 250 days in milk • Pregnancy exams used in prediction • 6% gain in REL of DPR for new bulls • Fertility used to predict longevity • 4% gain in REL of PL for recent bulls

  15. Selection for Longevity • Productive Life introduced in USA in 1994 to select for longevity • Genetic correlations with other traits: • Daughter pregnancy rate = .59 • Somatic cell score = -.35 • Udder composite = .30 • Daughter calving ease = -.24

  16. Holstein Pregnancy Rate - Phenotypic and Genetic Trend 1965-2000

  17. Value of Cow Fertility • Fertility expenses per day open • Heat detection ($20 / lact  .005) = $.10 • Semen ($15 / unit + $5 labor) *.025 = $.50 • Pregnancy exam ($10 / exam)*.012 = $.12 • Lactations too long or short = $.75 • Value of DPR as % of total economic value • 7% in Net Merit since August 2003 • 5% in TPI since February 2005, also • -2% for dairy form in TPI since February 2005

  18. Response to NM$ SelectionPercent of single trait response

  19. Heritability and Correlations Among Cow Fertility Traits Heritability on diagonal, USA data

  20. Cow Fertility TraitsEvaluated in Largest Holstein Populations

  21. Genetic Correlations of Traits Mark, 2003 EAAP meeting

  22. Days Open Genetic Correlations Jorjani, 2005 Interbull Bulletin DFS = Denmark-Finland-Sweden

  23. Conception Rate Genetic CorrelationsJorjani, 2005 Interbull Bulletin DFS = Denmark-Finland-Sweden

  24. Cow Fertility of Famous BullsAugust 2005 USA data

  25. Conclusions • Fertility traits are less heritable but more variable than yield and type • Selection for high yield reduces fertility • Selection for longevity increases fertility • Cow fertility traits receive 2% to 13% of total selection in many countries • Bulls that sire good fertility are available

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