Sire Summaries and Genetic Selection Flashcards
what is selection?
identifying the parents for the next generation
describe pedigree selection, give benefit and limitation
ancestors performances; is cheap but accuracy/sex limited
describe individual selection, give benefit and limitation
individual performance; is cheap, but sex limited and takes time
describe collateral relative selection; give benefit and limitation
full and half-sibs performance; is cheap but accuracy/sex limited and isn’t always available
describe progeny selection; give benefit and limitation
the ultimate source of information; and excellent indicator, but takes time and money
describe genomic selection; give benefit and limitation
an attempt to predict future performance based on aggregate of certain genetic contributions; has potential, but is only in the early stages of development
what is G + E = P?
genotype + environment = phenotype
what is heritability (h2)?
proportion of a trait (phenotype) readily transmitted from parent to offspring through additive gene action
for beef, what is the heritability of reproductive traits?
low (<0.20)
for beef, what is the heritability of growth traits?
moderate (0.20-0.40)
for beed, what is the heritability of carcass traits?
high (>0.40)
what are the relationships between beef traits like?
both positive and negative, need to watch closely when selecting
describe milk traits in terms of relationships and heritability?
nothing is super high in heritability, but most have positive relationships so will build on each other
redefine G + E = P for in terms of contribution of each factor, what is the take home message of this for beef and dairy?
G (h2 : 30%) + E (70%) = P
environment plays a much bigger role in beef cattle, since dairy is so well-controlled
what are sire summaries?
an estimate of genetic valus expressed as effects on production
what do breed associations do in terms of sire summaries?
- collect data from producers, other sources
- use defined traits of interest
- standardize information into distinct times/events for comparison pruposes
- compare results to average for the breed
- take into account genetic parameters (h2), sources and amount of information
- give phenotypic expectation as a result of using a particular sire
can the information from a breed association be used for all breeds of cattle?
no, only for the listed breed
what is REL% or ACC%?
reliability or accuracy: measure of how accurate the genetic estimate, the higher the reliability, the less deviation from the estimate
what are Dtrs/herds?
how many offspring from a sire
what does a higher birth weight result in?
higher dystocia
why does the accuracy of a sire summary lower as time goes on from birth weight?
not everything that is born survives to express the other traits like yearling weight, etc.
what is EPD?
expected progeny differency
what is maternal ability milk when referring to beef cattle?
the proportion of weaning weight influenced by production of dam
what is the first step in any selection practice?
identify your objectives
list and describe 4 dairy selection methodologies
- single traits: watch for negative and positive relationships
- indexes: select for multiple traits at once
- Net Merit $: bottom line production
- TPI (total performance index): balanced emphasis approach
what do you need to know before you can begin selection?
how your animals compare to the breed average
why are there constant changes in predicted values?
more information constantly coming out, increasing individual accuracy, changing breed averages, and changes in monetary values
what are the challenges with beef cattle selection? (5)
- environmental influences
- production objectives different for each sector (cow/calf, stocker, etc.)
- trait associations (some negative relationships)
- crossbreeding
- economic/practical challenges of AI for beef producers)
describe the use of sire summaries in dairy industry (6)
- few traits
- easy to measure
- limited environment effect
- most traits positive association
- limited crossbreeding
- AI highly feasible
describe the use of sire summaries in beef industry
- many traits select for
- easy to measure but may take time
- highly variable environment
- positive AND negative trait associations
- significant crossbreeding
- significant challenges with AI, but sire summaries can still be useful for selection or pruchase of new sires/bloodlines
