Dairy Cattle Genetic Evaluation

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Dairy Cattle Genetic Evaluation

• Production traits
• PTA predicted transmitting ability (like EPD)
• PPA predicted producing ability (like MPPA)
  females only (repeatability).
• Type traits
• STA standardized transmitting ability (standard
  deviation units)
• REL reliability (like ACC)

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Dairy Genetic Evaluation (Holstein)

• Production and Type in the USA
• Transmitting Abilities (PTAs) for type and
  production in the USA are calculated using animal
  model procedures.
• The Holstein Association USA computes the genetic
  evaluations for type traits.
• PTAs for production traits, Somatic Cell Score,
  Productive Life, and Net Merit are calculated by
  the US Department of Agricultures Animal
  Improvement Programs Laboratory (USDAAIPL).

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Dairy Genetic Evaluation (Holstein)

• Animal model evaluations are based on the animal
  and its relationships to other animals being
  evaluated.
• Information from the animal itself, its ancestors
  and its progeny is incorporated, with all known
  relationships among the animals considered.
• Cow family information is utilized, including
  records of all female ancestors and all female
  descendants.
• In an animal model evaluation, all identified
  relatives of an animal affect the animals
  evaluation. Additionally, each animal influences
  the evaluations of its relatives. The amount of
  influence depends on how closely the animals are
  related. Daughters, sons and parents have greater
  impact on an animals evaluation than do
  grandparents, cousins or other more remotely
  related animals.
• Statements are true for Genetic Evaluation of
  Species using Mixed Models (BLUP)

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GENETIC EVALUATION CHARACTERISTICS

• Many factors affect milk and type records.
• Management, environment, and genetics all
  influence an animals actual performance.
• The environment in which the cow performs must be
  accounted for (herd management effect).
• In addition, her actual records need to be
  standardized to account for the effects of age,
  season at calving lactation number and days open
  in the previous lactation.
• All records are standardized to 305day, mature
  equivalent basis.

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Dairy Genetic Evaluation

• Production and Type in the USA
• Some animals are also included in an
  across-country analysis (Interbull).
• Values are calculated as deviations from the
  base.
• The base for production traits was updated to
  cows born in 1995.

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Production Traits

• PTA M (lb milk)
• PTA F (lb fat)
• PTA F ( fat)
• PTA P (lb protein)
• PTA P ( protein)
• PTA PL (productive life, months)
• PTA SCS (somatic cell score lower better)

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Dairy Cattle

• Milk Yield (305-day) _
• PTA, lb Rel
• Bull A 1125 .66
• Bull B 2525 .92
• Future daughters of B are expected to produce
  1400 lb more milk per lactation than daughters of
  A, on average.

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Dairy Cattle

• Protein _
  
• PTA, lb PTA,
• Bull C 58 - 0.05
• Bull D 48 0.04

Correlation
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Genetic Evaluations for Productive Life, Somatic
Cell Score

• PRODUCTIVE LIFE
• Interested in measuring the genetic ability of a
  dairy cow to resist culling.
• Length of productive life is highly correlated
  with production and with linear type trait
  scores, particularly for the udder traits.
• PTAs for Productive Life were computed by
  combining genetic evaluations for productive life
  based on direct (Culling) and correlated traits
  (PTA for Production and Linear traits),
  respectively.

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Genetic Evaluations for Productive Life, Somatic
Cell Score

• The two components of PTA PL were calculated as
• a) Direct trait USDA-AIPL computed the direct
  measurement of productive life using culling
  data. Productive life is measured as total
  MONTHS-IN-MILK BY SEVEN YEARS OF AGE with a
  10-month maximum per lactation. No adjustment is
  made for level of milk production.
• b) Correlated traits The contribution of LINEAR
  TYPE to indirect prediction of productive life
  was calculated by the Holstein Association USA,
  while the indirect prediction of productive life
  from PRODUCTION TRAITS (MILK AND FAT) was
  calculated by USDA-AIPL. The indirect predictions
  from linear type traits and production traits
  were joined to produce PTAs for productive life
  based on indirect measurements.

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SOMATIC CELL SCORE

• The process used by USDA-AIPL to calculate PTA
  for Somatic Cell Score (SCS) is similar to that
  for calculating the PTAs for yield traits.
  Lactation average SCS for the first five
  lactations is edited and adjusted for calving age
  and season. An animals evaluation is calculated
  relative to cows born in 1995 and then is added
  to the average for first lactation SCS
  (standardized for age, calving month, and
  lactation length) of cows born in 1995. The
  average for Holsteins is approximately 3.1.

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SOMATIC CELL SCORE

• Using PTA SCS in an index is recommended so that
  appropriate selection might be given to improving
  MASTITIS RESISTANCE. Genetic selection to reduce
  SCS does not replace superior management and
  preventative care as the most effective means of
  controlling mastitis.
• Using PTA SCS in an index and placing 5 as much
  weight on SCS as on yield will help slow the
  increase in mastitis without sacrificing much in
  terms of increased yield.
• Reliabilities for PTA SCS are lower than for the
  yield traits because of a lower heritability (10
  vs. 25) and generally fewer daughter records
  with SCS data. Progeny-test bulls may attain 60
  reliability for PTA SCS. A high level of
  reliability will only be reached when second-crop
  daughters are added to a bulls proof.

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DAIRY LINEAR (TYPE) TRAITS EVALUATION

• Stature (height)
• Strength (frail vs. strong)
• Body depth
• Feet leg score
• Udder traits
• Others

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Linear Type Evaluations

• Linear type traits can help you breed a more
  profitable herd of Holsteins through selecting
  better bulls. Understanding linear type trait
  STAs can help you
• 1. identify the most important traits2. set
  realistic genetic goals for each trait3. select
  a better group of mating sires4. mate each cow
  to a complimentary bull5. accumulate genetic
  gains across generations

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Linear Type Evaluations

• The linear type trait genetic evaluations
  incorporate a multi-trait analysis. Multiple
  trait analysis increases the accuracy of the
  evaluations by considering the genetic
  correlations of the given linear trait with all
  other linear traits.
• Genetic evaluations for linear type traits are
  reported by Holstein Association USA as Standard
  Transmitting Abilities, or STAs.
• STAs rank an animal based on its genetic merit
  relative to the average cow born in 1995 in
  standard units.
• Since the bulls being actively marketed by AI
  organizations have been heavily selected for
  production and type traits, the AI bull
  population has a higher STA average for most
  linear traits compared to cows born in 1995.

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Interpreting Linear Type Trait - STAs

• Linear type trait genetic evaluations are first
  calculated as Predicted Transmitting Abilities
  (PTAs) similar to the production traits and then
  standardized to the range -3 to 3.
• Then all the traits can be displayed on the same
  graph. Additionally, Standardized Transmitting
  Abilities (STAs) allow you to easily compare
  different traits of the same bull and see which
  traits have the most extreme values.

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HERITABILITY OF TYPE TRAITS

• The degree to which a bull or cow is able to
  genetically influence various characteristics in
  its offspring is measured by heritability.
• It is difficult to make much genetic progress
  through selection and mating unless a trait has a
  heritability of .10 or higher.
• Table 3 contains estimates of heritability for
  linear traits currently summarized by the
  Holstein Association, USA.

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Standard Indexes

• LINEAR COMPOSITE INDEXES (Udder, body size, feet
  leg and dairy capacity composites)
• Net Merit
• Fluid Merit
• Cheese Merit
• TPI type/production index

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LINEAR COMPOSITE INDEXES

• Holstein Association USA linear composite indexes
  combine linear trait information on several
  related traits into one numerical value. This
  composite index can be used as a selection tool
  in breeding programs to identify those bulls
  which are predicted to transmit a desirable
  combination of the traits in the composite index.
  The traits included in each composite index are

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Udder Composite Index

• Udder Composite is computed as the total of the
  STAs of these six udder traits times their
  respective relative herd life weight (listed
  above).

• UDC (UD x .30)(FU x .16)(TP x .16)(UH x
  .16)(UW x .12)(UC x.10)

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Body Size Composite Body Size

• Composite is calculated from the four linear
  traits stature, strength, body depth and rump
  width. The calculation is
• (.5 x Stature) (.25 x Strength) (.15 x Body
  Depth) (.10 x Thurl Width)

• Every 1 STA increase in body size equals a 24
  pound increase in mature body weight. To put this
  in perspective, daughters of bulls that sire
  large cows (large positive evaluations for body
  size, 3.00) are expected to weigh 144 lb. more
  than those that sire small cows (large negative
  evaluations for body size, -3.00).

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Feet and Legs Composite

• The FLC formula utilizes a 5050 ratio of the
  three linear traits combined with the Feet and
  Legs Score. The three linear traits STAs are
  weighted

• .48 (Foot Angle) .37 (Rear Legs Rear View)
  .15 (Rear Legs Side View)
• The overall Feet and Legs Composite is
• FLC .5 (linear traits) .5 (Feet and Legs
  Score)

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NET MERIT

• Net Merit measures the additional net profit that
  an offspring of an animal will provide over its
  lifetime. Income and expenses for a typical dairy
  operation have been estimated, so that a measure
  of overall net profit can be calculated.

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NET MERIT

• Three different values (Net, Fluid and Cheese) of
  lifetime profitability are presented.
• The primary difference between the formulas is
  the emphasis that is placed on the components.
  Producers should select the index that is closest
  to the milk payment in your area.
• NET MERIT is based upon the future anticipated
  average milk price for all of the U.S.
• FLUID MERIT would be for producers who do not
  receive any payment for protein. In the Fluid
  Merit formula a negative value is placed on
  protein because additional feed is required to
  produce additional protein. Without a direct
  payment for the additional protein, this results
  in a negative value.
• CHEESE MERIT may be appropriate for farmers
  selling their milk directly to a cheese plant.
  More information about the new Net Merit may be
  found at the USDA website aipl.arsusda.gov.

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NET MERIT
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TPI Formula

• Key features of the new TPI formula
• 1. Places additional emphasis on pounds of fat,
  functional type and somatic cell score.
• 2. A protein fat ratio of 21 reflects the
  current multiple component prices.
• 3. Increased emphasis on Udder Composite, Overall
  Type and Somatic Cell Score coincides with a
  growing interest on health traits and those
  traits that are directly related to producing
  cows that will remain in the herd longer.Emphasis
  on each of the traits is listed below.

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Calving Easy

• This NAAB Calving Ease Sire Listing includes all
  Registered Holstein bulls with an official
  Calving Ease evaluation and either ACTIVE or
  LIMITED Semen Status. The average for all bulls
  with progeny evaluated is 8.3 DBH.

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Dairy Management Traits

• Milking speed
• Temperament
• Non-return rate

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Holstein Association Top 100 TPI International
Bulls February 2004
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29HO10124    BOLIVER