Methods of Selection Flashcards
What are the two sources of information we can use for selection?
Own performance and relatives
Define selection.
The process that determines which individuals become parents, how many offspring they produce, and how long they remain in the breeding population.
Selection should target _____________________ traits.
economically important
What are the three causes of genetic correlation?
-Gene linkage
-GEI
-Pleiotropy
What are the three basis of selection?
- Individual / Mass Selection
- Between families
- Within families
Define individual selection / mass selection.
Animals are selected based on their own performance.
What’s an advantage of mass selection?
Information can be easily available
Used when pedigree information is not available
Useful for traits expressed in both sexes
What is a disadvantage of mass selection?
Not applied for sex-limited or low heritability traits.
When heritability is _________, performance is a good indicator of BV.
high
Define family selection
Animals are selected based on the performance of their family.
Includes within, between and progeny test.
Define selection within families.
The best individuals within the families are selected.
Define selection between families.
All individuals within the best families are selected.
What is an advantage of family selection?
Improves traits with low heritability
Supports individual selection
What is a disadvantage of family selection?
Costly
requires large family size
Limits genetic diversity (potential inbreeding)
Define progeny test.
Selection of the individuals based on the average performance of their progeny.
What is an advantage of progeny test?
Best method for sex-limited traits and low heritability traits.
Increases accuracy of selection
Identifies carriers
What is a disadvantage of progeny test?
High cost and time
increases generation interval
requires an adequate number of progenies tested
What are the three methods of selection?
- tandem
- independent culling
- Total score / index of selection
Define tandem selection.
To improve a breeding population for several traits by selecting one trait for several generations, then focusing on improving the next trait, and so on.
Define independent culling levels.
A minimum cutoff off for each trait is fixed, and every animal to be selected must meet this minimum level for each of the traits under considerations.
Animals that do not meet these minimum levels are culled or removed.
Define total score / selection index
The ranking of animals is based on a value calculated by giving each selected trait a “relative weight”. This “weight” refers to the importance that a producer chooses to give a particular trait.
Define accuracy of selection.
A measure of the strength of the relationship between the true BVs and their predictions for a trait under selection.
What is Accuracy called in the dairy industry?
Reliability
Define True breeding value.
Represents the genetic potential of that animal.
Unknown value.
Cannot be observed directly.
How do you pronounce Accuracy in Portuguese?
Accooracy
Accuracy is represented by ____________.
r (TBV,EBV)
or BV with a “hat”
Accuracy ranges from ___ to ___.
0 to 1
The _________ the accuracy, the more likely EBV can predict TBV.
higher
What four factors influence the Accuracy of an EBV?
1) Amount of information, from animal itself and progeny
2) Heritability of the trait
3) Information on correlated traits
4) The accuracy of the parents
Accuracy increases with __________________.
number of records
Accuracy is higher for higher ____________ when number of progenies is the same.
heritability (h^2)
Do you go by EBV or Accuracy first?
EBV
If the EBVs are the same, you should pick the __________ accuracy one.
higher
