How do I decide what traits are important ? Selection Indices

1. How do I decide what traits are important ?Selection Indices Dorian Garrick Department of Animal Sciences Colorado State University

2. How do I decide ? • Not by looking at bulls and sire summaries Brown Bagger – Beef Cattle Genetics: Fine Tuning Selection Decisions

3. I decide what is important • By first looking at myself, my environment and my business • and considering likely future trends Brown Bagger – Beef Cattle Genetics: Fine Tuning Selection Decisions

4. Systematic Approach Breeding Objective Goal Selection Criteria Economic Analysis Breeding SchemeDesign Mating Plan Dissemination System Brown Bagger – Beef Cattle Genetics: Fine Tuning Selection Decisions

5. Systematic Approach Breeding Objective Goal Selection Criteria Economic Analysis Breeding SchemeDesign Mating Plan Dissemination System Brown Bagger – Beef Cattle Genetics: Fine Tuning Selection Decisions

6. Who are you? • Bull breeder • Actively involved in pedigree & performance recording • Have control over the nature & extent of performance recording on your animals • Bull buyer • Primarily interested in deciding which of the bulls on offer will give the greatest advance Brown Bagger – Beef Cattle Genetics: Fine Tuning Selection Decisions

7. Systematic Approach The purposeof change Breeding Objective Goal Selection Criteria Economic Analysis Breeding SchemeDesign Mating Plan Dissemination System Brown Bagger – Beef Cattle Genetics: Fine Tuning Selection Decisions

8. Goal • The purpose to which an endeavor is directed • We always want to increase utility (economic speak for satisfaction) • Most producers would be more satisfied if they could increase the profit of their ranch business Brown Bagger – Beef Cattle Genetics: Fine Tuning Selection Decisions

9. Goal • Profit is usually an important component of a business • Not the only component • Lifestyle, family values and environmental considerations are often an important part • If profit is not a component, we are probably dealing with a hobby rather than a business Brown Bagger – Beef Cattle Genetics: Fine Tuning Selection Decisions

10. Systematic Approach What to change & the value of change Breeding Objective Goal Selection Criteria Economic Analysis Breeding SchemeDesign Mating Plan Dissemination System Brown Bagger – Beef Cattle Genetics: Fine Tuning Selection Decisions

11. Breeding Objective • Sometimes called selection objective • Involves two components • A list of traits that influence the goal • Relative emphasis of each trait in the list • These quantify the extent to which you will compromise superiority in one trait for inferiority in another • Relative emphasis for a profit-based goals can be measured using relative economic values (REVs) Brown Bagger – Beef Cattle Genetics: Fine Tuning Selection Decisions

12. Breeding Objective • It is this list of traits that comprise the breeding objective that establishes the list of EPDs that should be of primary interest Brown Bagger – Beef Cattle Genetics: Fine Tuning Selection Decisions

13. Systematic Approach What tomeasure Breeding Objective Goal Selection Criteria Economic Analysis Breeding SchemeDesign Mating Plan Dissemination System Brown Bagger – Beef Cattle Genetics: Fine Tuning Selection Decisions

14. Selection Criteria • These are the animal characteristics that are physically recorded on individual animals in order to generate EPDs for each of the traits in the breeding objective • Some of these characteristics might be the actual trait of interest (eg sale weight) • Others may be indicator traits that are used to improve the prediction of EPDs in the breeding objective (eg scrotal circumference for female fertility) • We don’t need EPDs for selection criteria per se Brown Bagger – Beef Cattle Genetics: Fine Tuning Selection Decisions

15. Systematic Approach Breeding Objective Goal Selection Criteria Economic Analysis Breeding SchemeDesign Is this worthwhile Mating Plan Dissemination System Brown Bagger – Beef Cattle Genetics: Fine Tuning Selection Decisions

16. Economic Analysis • Consideration of the response to selection in relation to cost and effort • Bull breeders perspective • Does the effort of collecting additional selection criteria lead to significantly improved response relative to my goal • Bull buyers perspective • Does the benefit of using a more desirable bull/straw outweigh the purchase premium relative to an average bull Brown Bagger – Beef Cattle Genetics: Fine Tuning Selection Decisions

17. Production Circumstance • Cow-calf operation grazing rangeland and selling weanling cattle Brown Bagger – Beef Cattle Genetics: Fine Tuning Selection Decisions

18. Example Cow-Calf Goal • Maximize the total weight of sale weanling cattle crossing the cattle guard each year • Total weight = number sold x average weight Brown Bagger – Beef Cattle Genetics: Fine Tuning Selection Decisions

19. Example List of Traits • Birth Weight • Calving Ease • Sale (weaning) Weight • Direct and maternal components • Cow Maintenance Feed • Stayability • Heifer Pregnancy Brown Bagger – Beef Cattle Genetics: Fine Tuning Selection Decisions

20. See last years Brownbagger for consideration of the value of weaning weight (adjusting for cow maintenance increases) and stayability Brown Bagger – Beef Cattle Genetics: Fine Tuning Selection Decisions

21. Example List of Traits • Birth Weight • Calving Ease • Sale (weaning) Weight • Direct and maternal components • Cow Maintenance Feed • Stayability • Heifer Pregnancy Brown Bagger – Beef Cattle Genetics: Fine Tuning Selection Decisions

22. Relative Emphasis of Birth Weight & Calving Ease • What is the change in profit of a unit change in birth weight with other traits in the list held constant ? • No change in sale weight or calving ease • What is the change in profit of a unit change in calving ease with no change in birth weight ? Brown Bagger – Beef Cattle Genetics: Fine Tuning Selection Decisions

23. The Answer • Birth weight has no value in itself (it is simply an indicator trait) when both calving ease and sale weight are included in the breeding objective • Assuming birth weight is used as a correlated trait in multiple trait evaluations of calving ease and multiple trait evaluations of sale weight • The value of calving ease is influenced by its impact on the number of sale calves, veterinary costs (for the cow) and the cows subsequent performance Brown Bagger – Beef Cattle Genetics: Fine Tuning Selection Decisions

24. Example Selection Index • Includes EPDs only for those traits that are economically relevant • Those that have nonzero economic values • Does not exclude information from any useful selection criteria • Makes use of phenotypic data on indicator traits to improve the accuracy of EPDs for correlated economically relevant traits • Achieved through multiple trait evaluation Brown Bagger – Beef Cattle Genetics: Fine Tuning Selection Decisions

25. Summary • We can select on a measure of aggregate merit that directly relates to our business goal • By identifying the list of traits that influence our goal (EPD1, EPD2, EPD3) • By quantifying the relative emphasis appropriate for each trait in the list (r1, r2, r3) • By constructing the index values $index=r1EPD1 + r2EPD2 + r3EPD3 Brown Bagger – Beef Cattle Genetics: Fine Tuning Selection Decisions