SELECTION PART 2 Flashcards
What is a challenge in selection?
get a higher accuracy and intensity while decreasing GI
How to increase accuracy without taking time and money
- Use all performance records on all relatives
- Use BLUP methods for EBVs
- Incorporate genomic data
How to measure improvements?
Plot the response to selection = average EBV per year
How can we, animal breeders, make improvements?
Using reproductive technology such as AI and ET
2 ways for multiple trait selection
- You Select only for one trait can give you high yield
- Divide among several traits
What happens if we select for more traits
Selection intensity for each individual trait will decrease, but make greater improvements overall.
More traits gives us more or less response in individual traits
more traits gives less response in individual traits
Explain selection pressure on important traits
more selection pressure on important traits –> less pressure on less important –> ignore the worthless ones
What are the 4 methods to select animals
- tandem selection
- independent culling levels
- Selection for extremes
- Selection index
Selecting 1 trait each generation, alternating traits each generation
Tandem Selection
Select for 1 trait for a generation then switch, OR select for 1 trait until you reach a target then switch
Tanden Selection
Issue with tandem selection
ignore performance in other trait that may be good since you don’t measure that trait
Establish minimum levels of performance for each trait. Animals must meet the minimum for all traits to be selected.
Independent culling levels
Often used as part of multi-stage selection - make decisions at stages of the life cycle
Independent culling levels
What are the issues with independent culling levels (3 things)
- Translating goals into cutoff points is difficult
- changes of the cutoff must be made if population improves
- Does not allow excellence in one trait to offset poor performance in another trait
Select animals with high performance in any one trait, regardless of performance in other traits
Selection for extremes
Problem with selection for extremes
Lead to problems in other traits the animal has
Combines the performance for the traits into one aggregate number also known as index
Selection Index
How would you treat EBVs/EPDS in selection index
you treat the index as an EBV/EPD for selection
What is the problem of selection index
The economic value of the trait
What is the most important method of selection
Selection Index
Multi-Trait Selection
- Define the economic value for the trait
- Correlations among the traits
Which challenge is the most important to deal with
Define the economic value for the trait
What selection method can account for the multi-trait selection problems
Selection index
Why use several selection index
to make life easier
combination of economically important traits within a production system (it is the end, what you want to achieve)
Selection objective
traits based on which animals are chosen (they are the means used to achieve the selection objectives), what are you going to do
Selection criterion
The choice of the selection objective will depend on what
who your market is and what you are interested
The choice of the selection criteria will depend on 2 things
Its own economic importance/ the traits of economic relevance
The genetic and phenotypic variation that exist in the trait
Always thinking about the future
Selection objective:
