how do i decide what traits are important ? selection indices
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How do I decide what traits are important ? Selection Indices. Dorian Garrick Department of Animal Sciences Colorado State University. How do I decide ?. Not by looking at bulls and sire summaries. I decide what is important . By first looking at myself, my environment and my business - PowerPoint PPT PresentationTRANSCRIPT
1Brown Bagger – Beef Cattle Genetics:
Fine Tuning Selection Decisions
How do I decide what traits are important ?
Selection Indices
Dorian GarrickDepartment of Animal SciencesColorado State University
Brown Bagger – Beef Cattle Genetics:Fine Tuning Selection Decisions 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 ObjectiveSelection Criteria
DisseminationSystem
Economic Analysis
Goal
Breeding SchemeDesign
Mating Plan
Brown Bagger – Beef Cattle Genetics:Fine Tuning Selection Decisions 5
Systematic Approach
Breeding ObjectiveSelection Criteria
DisseminationSystem
Economic Analysis
Goal
Breeding SchemeDesign
Mating Plan
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
Breeding ObjectiveSelection Criteria
DisseminationSystem
Economic Analysis
Goal
Breeding SchemeDesign
Mating Plan
The purposeof change
Brown Bagger – Beef Cattle Genetics:Fine Tuning Selection Decisions 8
GoalThe purpose to which an endeavor is
directedWe 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
GoalProfit 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
Breeding ObjectiveSelection Criteria
DisseminationSystem
Economic Analysis
Goal
Breeding SchemeDesign
Mating Plan
What to change& the value of change
Brown Bagger – Beef Cattle Genetics:Fine Tuning Selection Decisions 11
Breeding ObjectiveSometimes 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
Breeding ObjectiveSelection Criteria
DisseminationSystem
Economic Analysis
Goal
Breeding SchemeDesign
Mating Plan
What tomeasure
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 ObjectiveSelection Criteria
DisseminationSystem
Economic Analysis
Goal
Breeding SchemeDesign
Mating Plan
Is this worthwhile
Brown Bagger – Beef Cattle Genetics:Fine Tuning Selection Decisions 16
Economic AnalysisConsideration of the response to selection in
relation to cost and effortBull 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