ARSBC 2018: EPDs and How to Use Them

Darrh Bullock
University of Kentucky

Crossbreeding should always be a consideration for commercial cattlemen. Crossbreeding has the greatest benefit for reproduction and other lowly heritable breeds.

Practical Guide to Bull Buying
Determine marketing strategy. Will heifers be retained? Make breeding decisions based on specific marketing plan. But, change marketing plan based on current situations.

It's pretty easy to find a bull that will give you great feeder calves and market animals. When we are keeping replacement females, we are now asking a bull to create females and feeder calves. We've given him a new job.

Determine your management level.
What is your labor? How frequently do you visit your cattle? How much attention do you give to them?
What is your level of nutritional management?
Assure that bulls are reproductively sound with a BSE.
Check for structural soundness. This is doubly important if you are retaining females.

The tough one is to set performance levels based on resource availability.

Select for performance using EPDs and indexes.
Determine other factors included horn/polled, color, tempermant, visual attractiveness.

"For trait for which EPDs are available that is the single piece of information you should be looking at," Bullock said. The other pieces of information including actual measurements, ratios, and genomics feed into the EPDs. Don't try to outsmart the system!

If you are looking at actual weights and EPDs together, you are reducing your ability to make accurate decisions. Just look at the EPD!

Environment is muddying the water. If we take it out we are improving the tool to make selection decisions.
EPDs is the best tool. Uses all information actual measurements, relatives, environment and genomics. EPDs are a risk management tool, they are not perfect.

One bull has an EPD of 65 lbs. Another has a 50 lbs EPD. The first bull's calves on average will weigh 15 pounds more.

Prior to EPDs, we basically had no opportunity to select for maternal traits. Maternal traits are predictions on the daughters of the bull.

American Angus Association started publishing EPDs in the early 1980s. Prior to EPDs there was success in increasing growth. Before EPDs you couldn't select for milk. The rate at which growth was increasing was faster with EPD selection. EPDs allowed us to select for increased growth and decrease birth weight (decreased calving problems).

All breeds have upward pressure for weaning weight. This increased growth is also increasing the mature size of cows. Mature height is under control, it has stayed flat. However, mature weight continues to increase. Mature height does not dictate nutrional requirements. Mature weight is what drives feed needs.

The trait we need to focus on is calving ease, not birth weight. Birth weight is simply an indicator of calving ease.

We need to be careful with selecting for more milk, or we will run into issues like we did with the frame race in the 1980s. Too much milk can lead to reproductive failure.

Most DNA variants (SNPs) have very small effects. But, when we add them all together they can have large effects.

Without a genomic test, accuracies are low. But, if we send in a DNA sample and do the DNA testing, it is the same as having 24 calving ease records out of that bull.

Calving Ease Direct is the tool to look for bulls that have calves that come easy. Calving Ease Maternal tells us if the heifer has the potential to calve unassisted.

Use EPD closest to marketing endpoint (weaning weight, yearling weight, carcass weight). Keep in mind correlated responses in calving ease, milk, and mature weight.

For maternal traits, watch for too much milk. There are Heifer Pregnancy, 30-Month Pregnant, Stayability and Sustained Cow Fertility for selection for reproduction.

Carcass traits are highly heritable and can make a lot of progress in first year of selection.

Selection indexes allows for comparison on a single value. Look for an index that matches what you are trying to do.

EPDs are breed specific. Different breed associations are continuously updating EPDs. Others are still updating on a twice a year basis.

Percentile rankings are one of the most under utilized tool in cattle selection. It is a great tool to find where in a breed a bull ranks.

Summary
Commercial bull buyesr should be practiciing crossbreeding
Best tools for selection are EPDs and indexes.

Link to video of Bullock's presentation: https://www.facebook.com/AngusJournal/videos/2146961142208480/

See ARSBC Newsroom for more information. http://www.appliedreprostrategies.com/2018/newsroom.html

Note: this post was live blogged and may contain errors.
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