Animal Breeding & Genetics Exam 2- Lecture 10: Large-Scale Genetic Evaluation

What is field data?  Explain the cooperative process of LGSE from the animal breeder to the calculation of EPDs.  You should discuss the role of registered animal producers/breeders, breed associations, animal breeding technologists/statisticians, and Best Linear Unbiased Prediction models.

Data that is collected from many breeders and processed by breed associations at a central location for LSGEs. Field data is collected from breeders and processed by breed associations. Technologists take processed data and use BLUP modeling to create comparisons across different herds.

Compare the extent of the utilization of LGSE across cattle, swine, sheep, goats, and horses.  Why is LSGE used more extensively in some of these species and not at all in others?

Horse racing was the first form of cross herd comparisons. Central testing of primarily males was initiated in swine, sheep, and cattle during the mid 1900s. Sire evaluations and the generation of estimated transmitting abilities known as EPDs began in the early 1970s.

From a rate of genetic progress standpoint, what two items does LSGE increase?

Selection intensity and accuracy of selection.

Explain what a central test station is and the type of information that is collected (phenotypic or genotypic?).  Are males or females more commonly tested?  Why? 

 

It is a station where young animals of different herds are fed a common diet at a central location. Males are more commonly tested.

Memorize the formula for a trait ratio and be sure you are able to calculate one if given an example.

(n/n)x100= ratio

What are the limitations of a central test station?  From an accuracy of selection standpoint, would a producer looking to buy a bull be better of using actual performance records or the EPDs of a bull to select which to purchase?

 

Comparisons are restricted to the measurements recorded during the test and are based only on the animals own performance. The ability to compare genetic merit is limited. Pre-test environments could alter performance results. Central tests have lost their justification with the advent of BLUP which can account for genetic and environmental differences within a contemporary group.

What is the difference between a parent and non-parent EPD?

Parent EPDs have EPDs with progeny data while non-parent EPDs don’t.

What four pieces of information are used to calculate EPDs? 

1. Animals actual performance

2. Performance of the animals progeny

3. Performance of other relatives

4. Genomic data

If a dam has a WW EPD of +30 and the sire has a WW EPD of +50 what would be the pedigree estimated EPD of the resulting offspring?

50-30=20 lbs

Explain the potential pitfalls of LSGE.

1. Faulty data- genetic evaluations are no better than the data contributing to it. Parental misidentification, falsification of performance records either deliberately or through estimations, incomplete reporting of poor records, and inaccurate environmental adjustments.

2. Improper contemporary grouping- animals aren’t treated alike but are reported from the same contemporary group, lack of relationship between animals in the contemporary group.

3. Genotype x environmental interaction- data for LSGE generally comes from diverse environments; this is not a problem unless an interaction exists. Causes reranking of individuals in a specific environment which BLUP can’t account for.