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Selection for Fertility in Dairy Cattle. Factors Affecting Fertility. Environment and management Season, region, herd, age, milk yield Calving difficulty, twins, mastitis, health Estrus detection and / or synchronization Voluntary waiting period Genes of cow (Daughter Pregnancy Rate)

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Selection for Fertility in Dairy Cattle

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Selection for fertility in dairy cattle l.jpg

Selection for Fertility in Dairy Cattle


Factors affecting fertility l.jpg

Factors Affecting Fertility

  • Environment and management

    • Season, region, herd, age, milk yield

    • Calving difficulty, twins, mastitis, health

    • Estrus detection and / or synchronization

    • Voluntary waiting period

  • Genes of cow (Daughter Pregnancy Rate)

  • Fertility of bull (ERCR)

  • Interaction of bull’s and cow’s genes


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Genetic Interactions

  • Lethal recessive genes

    • CVM aborts pregnancy 30-280 days

    • DUMPS aborts embryo at ~45 days

    • New defect causes loss at ~5 days

  • Inbreeding reduces fertility

  • Crossbreeding improves fertility

    • 1.8% increase in pregnancy rate


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USA Bull Fertility Evaluation

  • Measure of current semen fertility

  • Based on 1.6 million inseminations in last 3 years

  • Estimated Relative Conception Rate (ERCR) ranges +5% to –6%


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Bull Fertility ResearchKuhn, 2006

  • Moved evaluation to USDA from DRMS in Raleigh, NC in 2006

  • Data from eastern half of United States

  • Planning to use all services and pregnancy exams

  • Bull fertility is not correlated to daughter fertility (heifers or cows)


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Why Does Fertility Differ?

  • Male fertility includes

    • Ability of sperm to fertilize egg

    • Bull’s environmental conditions

  • Female fertility includes

    • Ability to cycle and show estrus

    • Ability of egg to conceive

    • Maternal support of embryo

    • Milk production stress (cows only)


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Heifer Fertility ResearchKuhn et al, 2006 J Dairy Sci 89:4907

  • Insemination records for 537,938 heifers in years 2003-2005

  • Average conception rate = 57%

  • Heritability = .5% (linear model), 1% (logistic model)

  • Genetic correlation = .39 with cow conception rate, -.19 with milk yield


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Heifer Fertility is Good

Paul VanRaden,

1995


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Problem: Cows Conceive LaterUSA Holsteins 1965-2000

Lactation

5th

4th

3rd

2nd

1st


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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


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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


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Sources of Fertility Data Percentages from 1998-1999 records


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Distribution of Days to ConceiveHolstein Calvings 1990 - 2001

Cows culled for reproductive reasons

≤ 50

≥ 250


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Seasonal Effects on FertilityHolsteins calving since 1997 in each USA region


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USA Cow 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


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USA Evaluation Methods

  • Animal model, introduced in 2003

    • Use same programs as other USDA traits

    • Compare cows within herd, season, and age

    • Convert to pregnancy rate (4 more days to conceive = 1% lower pregnancy rate)

  • Fertility parameter estimates used:

    • Heritability = 4%

    • Repeatability = 11%

    • Sire-by-herd interaction = 4%


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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 reliability of DPR for new bulls

  • Fertility used to predict longevity

    • 4% gain in REL of PL for recent bulls


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All-Breed Animal Model

  • Combined analysis of all breeds

  • Data from crossbreds included

  • Genetic differences among breeds are estimated

  • Planning to implement in May 2007


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Genetic Trends for Each BreedDaughter Pregnancy Rate, 1960-2000

+1.8% Heterosis


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Correlation of Yield and Fertility r = - .35


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Coefficients of Variation (CV)Standard deviation divided by mean


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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

    • 9% in Lifetime Net Merit

    • 5% in TPI, also

    • -2% for dairy form in TPI


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Cow Fertility Trait Heritabilities and Genetic Correlations

Heritabilities on diagonal


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Interbull

  • Provides international evaluations using data from 26 countries

    • Europe, North America, Australia, New Zealand, S. Africa, Israel, Japan

    • No South American countries yet

  • Office located in Sweden

  • Many traits are evaluated


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Countries with Most Holsteinsand Interbull abbreviations


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Fertility Traits and EmphasisIn Largest Holstein Populations


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Fertility Trait Indexes% of fertility emphasis

1Time from first to last insemination replaces non−return rate

2Countries that evaluate days to conception or calving interval


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Countries with Days to Conceptionand Interbull abbreviations


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Fertility Genetic Correlations Interbull test run, Sept. 2006


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Correlation of NLD and USA Fertility r = .91


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Genetic Correlations of Traits Mark, 2003 EAAP meeting


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Reporting of Daughter FertilityNational evaluation scales


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Days to ConceptionCorrelations with other traits


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Skewness


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Skewness of Fertility Evaluationswithin each country

  • Heifer conception rate

    • Range -.23 to .11

  • Days to first insemination

    • Range .09 to .33

  • Cow conception rate

    • Range -.20 to .10

  • Calving interval, days open, or DPR

    • Range .04 to .35, skewness in USA = .04


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Skewness of Fertility

  • Fertility trait data often have unusual distributions

  • Genetic evaluations are close to normally distributed

  • Standard linear models work well for large data sets


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Effects of Synchronization

  • Days to first insemination has less variation if herds synchronize heat

  • Sire rank for days to conception is similar in herds with heat detection or synchronization (Goodling et al, 2005 JDS)

  • DPR is adjusted for differences in herd variation


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Are Fertility Proofs Stable?

  • Bulls have about 100 daughters in first crop

  • Bulls later have thousands of daughters in second crop

  • How accurate are predictions?

  • Examined Select Sires bulls


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Top DPR Proof StabilitySelect Sires bulls born 1995-96, high reliability in 2006

DPR adjusted to 2005 base


Bottom dpr proof stability select sires bulls born 1995 96 high reliability in 2006 l.jpg

Bottom DPR Proof StabilitySelect Sires bulls born 1995-96, high reliability in 2006

DPR adjusted to 2005 base


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Daughter Fertility of Active Bulls

  • +1.8% DPR average for top 10%

  • –2.1% DPR average, bottom 10%

  • Difference = 16 days to conception

  • Reliability for bulls averages 63%


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Daughter Fertility of Famous BullsNovember 2006 USA scale


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Conclusions

  • Bulls with good fertility and daughter fertility are available

  • Cow fertility traits receive 1% to 13% of total selection in many countries

  • Select for fertility using an index

  • Fertility traits have lower heritability but more variation than yield and type

  • Management and genetics affect fertility


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Questions?


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