Breed and Trait Selection Considerations

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Breed and Trait Selection Considerations

• Dan W. Moser
• Dept. of Animal Sciences and Industry
• Kansas State University

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Outline

• Breed Selection Considerations
• General
• Seedstock-Specific
• Trait Selection Considerations
• General
• Commercial-Specific
• Seedstock-Specific

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Breed Selection Considerations

• Genetic Merit / Breeding Value
• Breed Complimentarity
• Specific Heterosis (Combining Ability)
• Uniformity of Offspring
• Maternal/Terminal Roles
• Breed Direction

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Breed Selection Considerations

• Genetic Antagonisms
• Genetic Evaluation
• Other Breed-Specific Services
• Market Realities and Perceptions
• Dynamic Nature of the Industry
• External Factors

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Genetic Merit of Breeds
Van Vleck and Cundiff, 2003
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Genetic Merit of Breeds

• Breeds differ for
• Maintenance
• Reproduction
• Carcass
• Genetic merit must match production environment.
• Some economically relevant traits go unmeasured.

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Unmeasured/Unreported Traits

• Mature cow size
• Reproductive data
• Feed intake
• Shear force

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Specific Heterosis

• A Lost Science?
• Not all heterosis is created equally
• Depends on the genetic similarity of the breeds
  being crossed
• Just as traits vary in heritability, traits also
  vary in effects of heterosis

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Specific HeterosisSurvival to Weaning, Direct,
AN CH GV HH LM
CH 2.01
GV 2.14 1.69
HH 2.52 2.77 3.49
LM 1.88 0.89 2.01 3.25
SM 1.28 1.05 1.12 2.82 1.28
Roughsedge et al., 2001
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Specific HeterosisPost Weaning Gain,
AN CH GV HH LM
CH 4.64
GV 4.94 3.91
HH 5.82 6.40 8.08
LM 4.35 2.06 4.64 7.51
SM 2.96 2.42 2.60 6.51 2.96
Roughsedge et al., 2001
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Specific HeterosisCow Fertility,
AN CH GV HH LM
CH 7.74
GV 8.24 6.52
HH 9.70 10.68 13.47
LM 7.25 3.44 7.74 12.52
SM 4.94 4.03 4.33 10.86 4.94
Roughsedge et al., 2001
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Breed Complimentarity

• Combine breeds to overcome antagonisms
• Not the best of both, but the average of both,
  plus heterosis

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Breed Complimentarity
Van Vleck and Cundiff, 2003
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Breed Complimentarity

• Rotational crossing using purebred sires that
  differ in biological type
• benefits from complimentarity
• reduces uniformity (across the calf crop)

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Breed Complimentarity

• Crossing purebred sires of different breeds but
  similar biological type
• improves uniformity
• reduces complimentarity
• may reduce effects of heterosis

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Breed Complimentarity

• Hybrids and composites have the ability to offer
  both complimentarity and uniformity
• Only a slight reduction in heterosis compared to
  using purebred sires
• All calves are same breed composition
• Also simplifies execution of the crossbreeding
  system

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Breed Selection Seedstock

• Rarely do seedstock operators completely change
  breeds.
• Opportunities exist to
• Add breeds
• Add F1s
• Add composites

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Evolution of Seedstock Production
Purebred, Single Breed
Purebred, Multi-Breed
Purebred (Multi-Breed) and F1
Purebred (Multi-Breed), F1, and Composite
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Weaning WeightGenetic Trend
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Maternal MilkGenetic Trend
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Trait Selection Considerations

• Economic Importance
• Heritability and Heterosis
• Method of Multiple Trait Selection
• Genetic Antagonisms
• Maternal/Terminal Roles
• Market Realities and Perceptions
• Dynamic Nature of the Industry

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Heritability

• Portion of a traits variation attributable to
  additive genetics
• In general, heritability is
• High for carcass traits and mature size
• Moderate for growth rate and milk production
• Low for reproductive traits

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Heritability

• Highly heritable traits are the easiest to change
  with selection
• Traits that are low in heritability can be
  changed with selection, but change is slower
• Heritability of a trait is reflected in the range
  of EPD across a population

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Heterosis
Trait HVI HVM HVP
Birth Weight 3.0 1.5 -
Weaning Weight 5.0 8.0 -
Calves weaned/cow exp. 3.0 8.0 5.0
Lbs. weaned/cow exp. 7.0 15.0 6.0
Feed Conversion (F/G) -1.0 - -
Age at Puberty -5.5 - -
Bourdon, 2000
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Heritability vs. Heterosis

• Logical for commercial producers to
• Select mainly for moderate and highly heritable
  traits
• Depend on heterosis to ensure adequate levels of
  traits low in heritability
• Seedstock producers cannot ignore traits that are
  low in heritability

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Methods ofMultiple-Trait Selection

• Independent Culling Levels
• Most commonly used
• Set min/max levels for each trait (EPD)
• Selection Index
• Most effective for overcoming antagonisms
• Weight traits (EPD) on economic importance

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Independent Culling Levels

• Possible to just miss some bulls that offer
  superior genetic combinations
• Limit the ability to overcome antagonisms

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Selection Index

• Fairly straightforward for terminal sires
• Much more complex for maternal lines
• Currently applied in other species, and for beef
  on other continents

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Selection Index

• Selection Index is fairly robust.
• Need the ability to enter index weights into sire
  sort web pages
• Or at least download sire summaries in a
  spreadsheet format.
• Precise economic weights are under development,
  are we ready to apply them?