Chapter 12: Large Scale Genetic Evaluation

Benefits of Large Scale Genetic Evaluation

allows genetic evaluation of whole populations

-i.e. breeds, animals from different herds or flocks

-increases selection intensity

Central Test

method of large scale genetic evaluation before BLUP

-all animals that were to be tested were to be brought to a single location where a feeding trial for the measurement of growth and feed efficiency was done

Downsides of Central Test

-only available for producers who could afford the cost of transportation

-testing stations were far away

-only tested for a few traits

-was only based on animal performance

-location bias (animals closer to the location were more likely to be tested)

1980s

BLUP first was used in the __________.

twice a year, daily

Before genomic information BLUP was only calculated _______________ now it is calculated __________.

designed tests, field data

When BLUP was first used data was collected during ____________ _________. Now, ____________ ___________ is collected and sent to breed associations or other organizations for evaluation.

Sire Summary

a list of genetic predictions, accuracy values, and other information about sires in a breed

-EPD, EBV, MPPA

Categories of Traits in Sire Summaries

direct and maternal

Direct Traits

measure of direct components

-growth potential of sire's calves at different ages

-performance attributable to genes inherited by the sireq

Maternal Traits

measure of maternal component of weaning weight

-predicts milking and mothering ability of sire's daughters

Total Maternal

a combination of direct and maternal traits for weaning weight

-overall ability of a sire's calf to produce weaning weight

-takes into account daughter's growth genes and her milking ability

1/2, all

Total maternal values can be calculated using ____ of the direct value and ____ of the maternal value.

Ways Weaning Weight is Affected

-calf's own genes- inherent ability to grow EPDww

-genes of calf's dam- nutritional environment (i.e.milk) EPDmilk

seperate

People are now trying to __________ milking and mothering ability.

EPDww

reflects the expected weaning weight performance of a bull's calves

EPDmilk

reflects the portion of expected weaning weight performance of a bull's daughter's calves influenced by her milking ability

Calving Ease Direct

reflects the number of unassisted birth's (%) of females who a bull is bred to

Calving Ease Maternal

reflects the number of unassisted births (%) of the bull's daughters

Accuracy Measures

measures of the relationship between trait values and their predictions

-sometimes referred to as the relationship between the real values and the predictions

Range of Accuracy Values

0 to 1

80%

An animal is considered proven when its accuracy value is _____ or higher.

Importance of Sire Summaries

increases effectiveness of selection

-expands pool of available sires (increases i)

-uses large amounts of data for genetic prediction

Reason we use Sire Summaries rather than Dam Summaries

-sire drives genetic change

-more accessible than dams (many straws from one ejaculate)

-many offspring

-A.I. makes using sires easier

-Managing selection risks- sires have higher acc.

-Marketing tools (i.e. select sires)

Interpreting Genetic Information

does not necessarily predict performance

-just because Bull A's EPD is +10 doesn't mean we expect his progeny to weigh 510lb at weaning when the average is 500

-predictions are used to compare individuals to one another

-prediction is not affected by accuracy

Example Prediction

Bull A EPDww= +10 and Bull B EPDww= -5

-We expect Bull A's progeny to be 15lb heavier on the average at weaning than Bull B's progeny when bred to similar females

Meaning of 0

depends on the statistical model and characteristics of data

-typically means the population average

breed adjustments

When working across breeds, you must use _____________ ___________.

Issues With Using Different Breeds

-different reference year

-different levels of breeding value

Base Year

the year that is used to determine the population average for traits

year

Sometimes EPDs are adjusted so that the base represents the average EPD of all animals born in a specific _____________.

Accuracy

gives information of selection risk and tells reliability of EPD

-high acc- little selection risk

-low acc- high selection risk

False

A low accuracy indicates that the EPD is wrong

Problems with Genetic Evaluation

-faulty data (pedigrees, performance records, adjustments, contemporary groups)

-connectedness

-GxE interactions

Connectedness

relationships in different groups- related individuals in different group

-more is better

- AI makes this easier

Pedigree Faulty data

i.e. parental misidentification

-less emphasis as progeny increases

Performance Record Faulty data

-falsifying records

-incomplete recording- most common

Example of Wrong Adjustments

animal's birthday is in the wrong month

Contemporary Groups Faulty Data

-reported as members of the wrong group

-treatment differences

GxE Interactions

significant interaction can cause problems

-lowly heritable traits are most susceptible