Selection Systems Flashcards
who is selected
individuals
relative - ancestors, siblings and progeny
how are they selected
independent culling levels
tandem selection
index of weighted traits
what are correction factors?
sex
age of dam
age of calf
singleton vs twin
what is individual selection based on
animals own performance
practicle if trait is measurable and expressed early
what is ancestral selection based on
weighted average of ancestors
father counts more then grandfather
useful if trait is not expressed early
when do you use ancestral selection
- when individual is not available
- use at least one relative on both the dam and sire side of the pedigree (same relatives for each individual)
- use closest relative available
use mean of relatives if theres many records
what is the genetic selection of a horse
long generation
few offspring
late mating
training is a cofounding factos
improvement is slow
what is genetic selection for dogs and cats
obedience tests
traiing is also a confounding factor
ancestral selection
progeny or sub selection (littler success, breeders should maintain contact and follow up)
how is selection typically done?
need to select for more than one trait
negative traits doesnt mean detrimental and positive doesnt mean bene ficial
how does genetic correlation effect meat quality?
marbling score and backfat thickness, lean yeild and shear force
marbling is good the more abundent the better
what are independent culling levels
select for minimum value per characteristic, no averaging
useful for multipurpose animal
potentially cull many animals
what is ROP bulls?
record of performance
30 cm scrotal circumference
pass on feet and legs
above average weight gain for breed
how do you choose to rebreed a cow in the herd?
they must produce a calf
must mother well to that calf
must not be dangerous (have temperament problems
What is tandem selection?
seelcting for most important trait this season and second most important trait next season
when is tandem selection efficient ?
if all desired traits are positively correlated
BUT- in reality used primarily as a temporary selection to focus on the most important trait
what is index selection?
use a formula to simultaneously select for several traits, emphasizing some more than others
what is indirect selection?
use of a correlated trait to select for another trait
When is indirect selection useful?
traits that are difficult to measure
traits with low hieratability but high relevancy
What does response to selection depend on?
generation interval
selection intensity
variation in population
hieratability of trait
accuracy of selection
effective population size
what is generation interval?
average time in years between when an animal and its replacement are born
affected by: gestation length, age at puberty and like sex replacement
what is selection intensity
average proportion of animal selected
fewer males kept then females
smaller proportion of litter bearers
based on animals kept - expressed as a standard deviation
what is variation selection diferences
change in lb, litter size
its a selection group vs the total group
what is hieretability?
the likelyhood of offspring developing a trait from parentage
what is accuracy of selection?
ranges from 0-1 and depends on
method of selection and number of measurements
what is effective population size
must be large enough to avoid inbreeding ans to maintain variation for selection
what is genetic gain?
genetic improvement over time
how do you increase genetic gain
increased selection intensity (select fewer but it may decrease genetic variety)
increase accuracy of selection(use individuals instead of pedigree)
increase genetic variation - introduce new quality stock
decrease generation interval - harvesting embryos = very expensive
what is compare to contemporaries
doesnt really measure improvement
does assess position in industry
see how past animal test and then see how many animals in total have the genetic progress
what is improvement over time
compare offsprings performance to parents
compare herds performance over many years
what is a repeat mating design
compare new bull to old bull - breed young females with old bull and old females with young bulls
transport stored emyros and fresh embryos in one season
compare performance of calves
what happens if there is no progress
you hit a plateau
that is the peak of that progress
now it cant grow without serious fertility problems
