1. Brown Bagger – Beef Cattle Genetics: Fine Tuning Selection Decisions 1 How do I decide what traits are important ? Selection Indices Dorian Garrick Department of Animal Sciences Colorado State University

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

3. 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

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

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

6. 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

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

8. 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

9. 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

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

11. 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)

12. 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

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

14. 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

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

16. 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

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

18. 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

19. 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

20. 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

21. 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

22. 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 ?

23. 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

24. 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

25. 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 (EPD 1, EPD 2, EPD 3 )  By quantifying the relative emphasis appropriate for each trait in the list (r 1, r 2, r 3 )  By constructing the index values $index=r 1 EPD 1 + r 2 EPD 2 + r 3 EPD 3