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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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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




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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