Sire Summaries and Genetic Selection

Question 1

what is selection?

Answer 1

identifying the parents for the next generation

Question 2

describe pedigree selection, give benefit and limitation

Answer 2

ancestors performances; is cheap but accuracy/sex limited

Question 3

describe individual selection, give benefit and limitation

Answer 3

individual performance; is cheap, but sex limited and takes time

Question 4

describe collateral relative selection; give benefit and limitation

Answer 4

full and half-sibs performance; is cheap but accuracy/sex limited and isn’t always available

Question 5

describe progeny selection; give benefit and limitation

Answer 5

the ultimate source of information; and excellent indicator, but takes time and money

Question 6

describe genomic selection; give benefit and limitation

Answer 6

an attempt to predict future performance based on aggregate of certain genetic contributions; has potential, but is only in the early stages of development

Question 7

what is G + E = P?

Answer 7

genotype + environment = phenotype

Question 8

what is heritability (h2)?

Answer 8

proportion of a trait (phenotype) readily transmitted from parent to offspring through additive gene action

Question 9

for beef, what is the heritability of reproductive traits?

Answer 9

low (<0.20)

Question 10

for beef, what is the heritability of growth traits?

Answer 10

moderate (0.20-0.40)

Question 11

for beed, what is the heritability of carcass traits?

Answer 11

high (>0.40)

Question 12

what are the relationships between beef traits like?

Answer 12

both positive and negative, need to watch closely when selecting

Question 13

describe milk traits in terms of relationships and heritability?

Answer 13

nothing is super high in heritability, but most have positive relationships so will build on each other

Question 14

redefine G + E = P for in terms of contribution of each factor, what is the take home message of this for beef and dairy?

Answer 14

G (h2 : 30%) + E (70%) = P

environment plays a much bigger role in beef cattle, since dairy is so well-controlled

Question 15

what are sire summaries?

Answer 15

an estimate of genetic valus expressed as effects on production

Question 16

what do breed associations do in terms of sire summaries?

Answer 16

1. collect data from producers, other sources
2. use defined traits of interest
3. standardize information into distinct times/events for comparison pruposes
4. compare results to average for the breed
5. take into account genetic parameters (h2), sources and amount of information
6. give phenotypic expectation as a result of using a particular sire

Question 17

can the information from a breed association be used for all breeds of cattle?

Answer 17

no, only for the listed breed

Question 18

what is REL% or ACC%?

Answer 18

reliability or accuracy: measure of how accurate the genetic estimate, the higher the reliability, the less deviation from the estimate

Question 19

what are Dtrs/herds?

Answer 19

how many offspring from a sire

Question 20

what does a higher birth weight result in?

Answer 20

higher dystocia

Question 21

why does the accuracy of a sire summary lower as time goes on from birth weight?

Answer 21

not everything that is born survives to express the other traits like yearling weight, etc.

Question 22

what is EPD?

Answer 22

expected progeny differency

Question 23

what is maternal ability milk when referring to beef cattle?

Answer 23

the proportion of weaning weight influenced by production of dam

Question 24

what is the first step in any selection practice?

Answer 24

identify your objectives

Question 25

list and describe 4 dairy selection methodologies

Answer 25

1. single traits: watch for negative and positive relationships
2. indexes: select for multiple traits at once
3. Net Merit $: bottom line production
4. TPI (total performance index): balanced emphasis approach

Question 26

what do you need to know before you can begin selection?

Answer 26

how your animals compare to the breed average

Question 27

why are there constant changes in predicted values?

Answer 27

more information constantly coming out, increasing individual accuracy, changing breed averages, and changes in monetary values

Question 28

what are the challenges with beef cattle selection? (5)

Answer 28

1. environmental influences
2. production objectives different for each sector (cow/calf, stocker, etc.)
3. trait associations (some negative relationships)
4. crossbreeding
5. economic/practical challenges of AI for beef producers)

Question 29

describe the use of sire summaries in dairy industry (6)

Answer 29

1. few traits
2. easy to measure
3. limited environment effect
4. most traits positive association
5. limited crossbreeding
6. AI highly feasible

Question 30

describe the use of sire summaries in beef industry

Answer 30

1. many traits select for
2. easy to measure but may take time
3. highly variable environment
4. positive AND negative trait associations
5. significant crossbreeding
6. significant challenges with AI, but sire summaries can still be useful for selection or pruchase of new sires/bloodlines