Animal breeding 3
Terms
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- heritability
- a measure of the strength of the relationship between performance and breeding values for a trait in a population
- If a trait is highly heritable?
- animals with high performance tend to produce high performance animals or low performance produce low performance offspring
- If a trait is not highly heritable...
- then performance records of parents reveal little about progeny performance.
- _________ traits breeding values have a large influence on phenotypic values (i.e. performance)
- Highly heritable
- Below _______ are considered lowly heritable
- .2
- Between _____ and _____ are considered moderately heritable.
- .2 and .4
- Above _______ are considered highly heritable
- .4
- Example of lowly heritable?
- Survivability and fertility
- Examples of medium heritable?
- production traits (milk output, speed, etc)
- Examples of highly heritable?
- Chicken egg size, production related to skeletal dimensions.
- Heritability is a __________ measure.
- Population
- repeatability
- a measure of the strength of the relationship between repeated records for a trait in a population.
- repeatability is a ___________ between repeated records for a trait.
- correlation
- repeatability ranges from ___ to ___
- -1 to +1
- Environmental uniformity
- manage animals such that environmental effects on the performance of different animals are as similar as possible
- Adjusted weaning weight = ?
- (Actual weight - Birth weight) / age of weighing x 205 + Birth Weight + Age of dam factor
- Contemporary group
- a group of animals that have experienced a similar environment with respect to the expression of a trait.
- Contemporary group can be defined by...
-
breeder
year
season of year
sex
feeding program
pasture
puling contest
race
class in a show
- Contemporary groups are most commonly used to account for those environmental differences between groups that cannot be __________
- quantified
- Trait ration
- expression of relative performance
- Trait ratio calculation
- specific weight/average weight x 100
- single trait selection
- selection for just one trait (rarely done)
- multiple trait selection
- selection for more than one trait
- aggregate breeding value
- the breeding value of an individual for a combo of traits
- tandem selection
- selection first for one trait, then another
- selection target
- is a level of breeding value considered optimal in an absolute or practical sense
- favorably correlated
- selection for one trait will improve another
- unfavorably correlated
- selection for one trait will cause a slide in the other
- independent culling levels
- minimum standards for traits undergoing multiple trait selection, animals failing to meet any one standard are rejected regardless of merit in other traits
- repeated back crossing
- (Introgression) is a mating system used to incorporate an allele or alleles existing in one population to another population
- back crossing
- mating of a hybrid to a purebred or a parent breed or line
- Top Crossing
-
aka Grading up
a mating system designed to create a purebred population by mating successive generations of non purebred females to purebred sires.
a mating system designed to convert a population from one breed to another by mating successive generations of non purebred females descended from the first breed to sires of the second. - Define a mating system
- set of rules for making mating decisions, no limit to them
- Random mating
- a mating system which mates are chosen at random
- assortative mating
- mating of similar individuals or dissimilar; requires more data or a plan and animals are typically ranked
- Economic selection index
- combo of weighing factors and genetic ifno on more than one trait
- Economic index looks like
-
I = b1x1 + b2x2+...bnxn
I = an index value or genetic prediction
b1 = weighing factor
x1 = single item or evidence - breeding objective
-
H = v1BV1 + v2BV2 +... vnBVn
H = aggregate BV
V1 = economic weight for a trait
BV = breeding value for a trait in the breeding objective - phenotypic selection index
- a form of economic selection index used where selection is strictly phenotypic selection