Longevity and fertility
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Longevity and Fertility. History of Productive Life. January 1994 – Single-trait PL for bulls July 1994 – Multi-trait PL at HA for all bulls January 1995 – Base change of 0.9 months January 1996 – Cow PL PTA’s first published August 2000 – New multi-trait methods at USDA

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Longevity and Fertility

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Longevity and fertility

Longevity and Fertility


History of productive life

History of Productive Life

January 1994 – Single-trait PL for bulls

July 1994 – Multi-trait PL at HA for all bulls

January 1995 – Base change of 0.9 months

January 1996 – Cow PL PTA’s first published

August 2000 – New multi-trait methods at USDA

August 2000 – Base change of 0.8 months

November 2000 – Genetic correlations reduced


Pta productive life

PTA Productive Life

  • Productive Life (PL) =

    Total months in milk by seven years of age, including up to 10 months per lactation.

  • Multi-trait PL includes correlated traits

    • Milk, fat, protein

    • SCS

    • Type composites (udder, feet & legs, size)

    • Cull rate gradually replaces correlated traits


Calculation of multi trait pl

Calculation of Multi-trait PL

PTA PL = PA PL + Cov(true PL – PA, PTA – PA) Var -1(PTA – PA) (PTA – PA)

Begin with PA, regress on PTA – PA

  • Direct (single trait) PL and 7 indirect traits included in vectors

  • Weight on PTA – PA for each trait is determined by correlations, heritabilities, and reliabilities

    Decline to zero as single-trait REL for PL approaches 99%


Heritabilities and correlations

Heritabilities and Correlations

Genetic Correlation above diagonal

Heritabilities on the diagonal(for Holsteins)

Phenotypic Correlation below diagonal


Example data for pl

Example Data for PL

aPTA is single trait, PA is multi-trait

bRELPA max = 50%


Example weights for pl

Example Weights for PL

aPTA is single trait, PA is multi-trait

bRELPA max = 50%


Stability of pl evaluations

Stability of PL Evaluations

  • Update of 1997 study by Ryan Starkenburg

  • August 2001 evaluations compared for:

    • January 1995 active AI bulls

    • February 1997 active AI bulls

  • PTA protein adjusted to true protein

  • Bulls with sample code ‘0’ excluded

  • August 2001 PL reliability  90%

  • Regressions (expected to be 1)

  • Correlations (hoped to be high)


High pta pl bulls from 1995

High PTA PL Bulls from 1995

1January 1995 Evaluation

2August 2001 Evaluation


Low pta pl bulls from 1995

Low PTA PL Bulls from 1995

1January 1995 Evaluation

2August 2001 Evaluation


High pta pl bulls from 1997

High PTA PL Bulls from 1997

1February 1997 Evaluation

2August 2001 Evaluation


Low pta pl bulls from 1997

Low PTA PL Bulls from 1997

1February 1997 Evaluation

2August 2001 Evaluation


Current and past evaluations regressions and correlations

Current and Past EvaluationsRegressions and Correlations


Pl and lifespan defined

PL and Lifespan Defined

  • PL

    • Credit for maximum 10 mo per lactation

    • Records  305d weren’t stored in database

    • Long calving intervals unprofitable

  • Lifespan

    • Credit for months between lactations

    • Higher yield and bST allow longer lactations

    • Embryo donors not penalized


Lifespan and pl compared

Lifespan and PL Compared

  • Heritability

    • 6.7% for lifespan

    • 7.6% for PL

    • (8.5% official PL estimate since 1994)

  • Genetic correlations of lifespan

    • .986 with PL

    • More correlated than PL with yield

    • Less correlated than PL with SCS

    • Less correlated with fertility (-.46 vs -.59)


Cow fertility

Cow Fertility

  • Days Open

    • Calving interval – 280 days

    • Lower limit of 50 days, upper limit 250

    • Sold for reproductive problems = 250

  • Genetic parameters

    • 3.7% heritability

    • .32 correlation with protein

    • .30 correlation with SCS


Bulls with low daughter fertility

Bulls with Low Daughter Fertility


Bulls with high daughter fertility

Bulls with High Daughter Fertility


Foreign longevity evaluations

Foreign Longevity Evaluations

  • Measures of longevity:

    Survival, herd life, stayability, durability, PL

  • Most countries adjust for yield

  • Evaluated in 13 Countries:

    Australia, Austria, Canada, Denmark, France, Germany, Great Britain, Israel, Italy, Netherlands, New Zealand, Sweden, Switzerland, USA


Foreign bull productive life

Foreign Bull Productive Life

  • Options

    • Set PL equal to zero or breed average

    • Simple regressions on yield (1995-2000)

    • Use parent average from domestic PL data (August 2000)

    • Combine PA with Interbull yield and type (November 2000)

    • Include also Interbull SCS (May 2001)

    • MACE for longevity (Dutch research)


Conclusions

Conclusions

  • Longevity rankings have high value but lower accuracy than other traits.

  • Cow fertility has low heritability (3.7%) but high genetic correlation with PL (-.59).

  • Selection on PL is effective, but cow fertility evaluations could increase lifetime profit. Credit for embryo donors may be needed.


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