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Breed and Trait Selection Considerations

Breed and Trait Selection Considerations. Dan W. Moser Dept. of Animal Sciences and Industry Kansas State University. Outline. Breed Selection Considerations General Seedstock-Specific Trait Selection Considerations General Commercial-Specific Seedstock-Specific.

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Breed and Trait Selection Considerations

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  1. Breed and Trait Selection Considerations Dan W. Moser Dept. of Animal Sciences and Industry Kansas State University

  2. Outline • Breed Selection Considerations • General • Seedstock-Specific • Trait Selection Considerations • General • Commercial-Specific • Seedstock-Specific

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

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

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

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

  7. Unmeasured/Unreported Traits • Mature cow size • Reproductive data • Feed intake • Shear force

  8. 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

  9. Specific HeterosisSurvival to Weaning, Direct, % Roughsedge et al., 2001

  10. Specific HeterosisPost Weaning Gain, % Roughsedge et al., 2001

  11. Specific HeterosisCow Fertility, % Roughsedge et al., 2001

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

  13. Breed Complimentarity Van Vleck and Cundiff, 2003

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

  15. Breed Complimentarity • Crossing purebred sires of different breeds but similar biological type: • improves uniformity • reduces complimentarity • may reduce effects of heterosis

  16. 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

  17. Breed Selection: Seedstock • Rarely do seedstock operators completely change breeds. • Opportunities exist to: • Add breeds • Add F1’s • Add composites

  18. Evolution of Seedstock Production Purebred, Single Breed Purebred, Multi-Breed Purebred (Multi-Breed) and F1 Purebred (Multi-Breed), F1, and Composite

  19. Weaning WeightGenetic Trend

  20. Maternal MilkGenetic Trend

  21. 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

  22. Heritability • Portion of a trait’s 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

  23. 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

  24. Heterosis Bourdon, 2000

  25. 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

  26. 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

  27. Independent Culling Levels • Possible to “just miss” some bulls that offer superior genetic combinations • Limit the ability to overcome antagonisms

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

  29. 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?

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