Breeding Values Flashcards
what is a breeding value
number that represents the value as a parent
the deviation of the animals progeny compared to the average reference population
what does the value depend on
the average performance of the referene population
the value of the alleles that each progenitor can transfer to its progeny
how do you get phenotype
phenotype = genotype + environment
genotype - additive effects - dominance deviation, interactive effects
environment - feeding housing health and stress
why alter a phenotype
improve environent
change genotype
look to meausre how much changing the genotype would help
why should the genotypic value be calculated?
based on breeding a bull to a wide variety of cows, ideally in a wide variety of herds in many environments gives the cows the best chance at genetic change
what is a breeding value?
is a measure of the animals expected progeny performance relative to population mean
- twice the average deviation of the animals offspring from the mean
- twice becasue onlt 1/2 is being measured from one parent
what is breeding value affected by?
gene frequency
type of gene act
difference in genotypic value between the homozygotes
( not constant can be altered through selection)
is it possible to estimate an animals true breeding value?
no but you can estimate = EBV
what is EPD
expected progeny difference
expected differenc in performance of a bulls progeny when compared to the average progeny performance of all bulls evaluated
expressed relative to other animals - in same population and breed
how do you calculate EPDs
animals own performance
pedigree
progeny records
what is the difference between EBV and EPV
there is not much difference except mathmatecally EPV is 1/2 the EBV
what does the national cattle evaluation account for
pedigree relationships
herd location differences
managment differences
relationships between traits
what are maternal EPDs
sires milk EPD is expressed as additional pounds of calf weaned by his daughters due to milk
expressed in sires grand progeny
what helps with EPV accuracy
measure of reliability
indicator of risk
increases as more information is used to calculate EPD
