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Livestock Improvement through Selection

Livestock Improvement through Selection. Learn all genetic traits!!!!. Objectives. Compare and contrast the idea of genetics vs environment List examples of high and low heritability estimates Define expected progeny differences Describe the importance of livestock improvement. Overview.

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Livestock Improvement through Selection

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  1. Livestock Improvement through Selection Learn all genetic traits!!!!

  2. Objectives Compare and contrast the idea of genetics vs environment List examples of high and low heritability estimates Define expected progeny differences Describe the importance of livestock improvement

  3. Overview • Emphasis on certain traits depend on • Economic importance • Rate of improvement of specific trait • Factors affecting the rate of improvement • Heritability • Selection differential • Generation interval • Expressions of traits are influenced by genetics and environment

  4. Genetics vs Environment • Different factors affect growth in different ways • How can we tell the difference? • Contemporary trials

  5. Heritability • An estimate of the fraction of the phenotypic superiority or inferiority • Ex: low heritability estimates (.10-.20) 80 -90% of variation is due to environmental factors • Low heritability traits change slowly

  6. High vs Low Heritability • Low heritability • Reproductive traits • Fertility • Calving interval • Litter size ** greatest effect on economic return!! • High heritability • Carcass traits • Fat thickness • Rib eye area • Efficiency of gain ** small effect on economic return!!

  7. Heritable trait example Qualitative – hair color Quantitative – performance traits Single trait – eye color, hair color Multi trait – calving ease, speed

  8. Expected Progeny Differences • EPD – the expected (or predicted) difference in performance between the progeny of two animals of the same breed. • Most accurate method of comparing breeding value • Accounts for • Individual’s, parent’s, sibling’s and progeny’s performance

  9. Advantages of EPD’s Most accurate predictors of progeny performance Provide an accurate depiction of an individual/herd’s strength/weakness Allow for greater specificity in multi-trait selection

  10. Selection Index Place added emphasis on the more economically important traits

  11. Visual Aids There’s an app for that!

  12. Visual Aids Frame score

  13. Visual Aids Hip Height

  14. Visual Aids • Ultrasound Technologies • Done in real time • Cross-section of rib eye • Back fat and REA

  15. Objectives Compare and contrast the idea of genetics vs environment List examples of high and low heritability estimates Define expected progeny differences Describe the importance of livestock improvement

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