Monday, August 7, 2017

TBCSC 2017: Genomic Enhanced Expected Progeny Difference -Do they Work?

John Genho
Livestock Genetic Services

Livestock Genetic Services does genetic evaluations for several American (eared) breed associations.

When comparing EPDs and raw performance, the relationships are always better when using genomic information, compared to pedigree information only.

King Ranch marketed a bull named KR Ricardo 182/20.
KR Ricardo 182/20
This bull had four brands on his shoulder. Two stars, as he had two copies of the favorable DNA variant (allele) for the GeneStar Marbling test and two T for the GeneStar Tenderness tests. Now that we use 50,000 DNA markers, branding is not really practical!

As we adjust

Sometimes we see that calf, and the cow looks mad, so you say, that calf looks like 80 lbs. Or, you don't take the time to collect weaning weights and yearling weights.
How can geneticists adjust bad data? We can't. If you want better EPDs, you need to turn in clean data!

What if Genho went in for a physics and IQ test. The first time he went in, Albert Eistein and Stephen Hawking were the two others taking the test that day. He looks like he is 30 points below average on that day. He decides to go in for a second test. On this day, his contemporaries are Justin Beiber and Homer Simpson. On this day he scores 30 points above average! Did Genho's intelligence change between these days? No. But his contemporary group did. We need to make sure that we have large and well formed contemporary groups. Contemporary groups are formed using breeder, year, age and other information. However, breeders control how contemporary groups are formed.
1. Breeders can report management groups.
Calves that are managed differently (different pastures, some being fitted for show) need to be reported as different contemporary groups.
2. Breeders can control which calves are reported.
When the bottom of the calf crop is not reported, the middle of the calf crop (contemporary group) looks like it is below average. The middle of the group looks like poor performers, because the poor performers weren't reported!

"We get excited about this new model and this new test. What we need to do is make sure we collect clean data." says Genho. We need to make sure that we are reporting complete, clean data.

We can remodel a house with a hammer, hand saw, and screwdriver. Or, we can remodel a house with a circular saw, pneumatic air gun, and electric driver. We can remodel the house much quicker with modern tools. It is still important to be a good breeder. The more powerful tools mean we need to be better breeders.

Decker's Take Home:
Trust EPDs and use them. And, just as important, turn in clean and complete data.

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