Calving Ease EPD – What does it tell us and what is the use case scenario?

We just finished talking about Birth Weight EPD, so Calving Ease (CE) seems like the perfect one to tackle next.

According to ASA/IGS, Calving Ease Direct (CED) is reported as the difference in probability of calves being born unassisted out of first-calf heifers. Higher values are more favorable.

Angus defines Calving Ease Direct similarly: it is expressed as a difference in percentage of unassisted births and predicts the average difference in ease with which a sire’s calves will be born when he is bred to first-calf heifers.

Now, let’s boil that down.

If you’re looking for a bull to use on first-calf heifers, CE is designed to help answer a pretty practical question: Which bull is more likely to sire calves that are born unassisted?

Remember our birth weight discussion? BW EPD predicts differences in pounds of birth weight. CE predicts differences in the probability of an unassisted birth.

Birth weight certainly can play a role in calving difficulty, but it isn’t the outcome itself. That’s why if the goal is specifically to reduce calving difficulty in heifers, CE gets us closer to the question we’re typically trying to answer…what bull is most likely to be safest to use on my heifers?

So…how do we compare bulls using CE?

Let’s say we’re comparing two bulls within the same breed:

Sire A = +17 CE

Sire B = +12 CE

There’s a 5-point difference between them.

If comparably mated to first-calf heifers, Sire A would be expected to sire 5 percentage points more unassisted births than Sire B, on average.

Another way to think about it: if each bull were bred to 100 comparable heifers, we’d expect approximately five more unassisted births from Sire A’s group than Sire B’s group. Remember, though, this is a prediction across a group of calves. It doesn’t mean every calf by the +17 bull will come unassisted, or that every calf by the +12 bull will require help. Remember, the sire isn’t the only piece of the equation here either…the dam’s genetics and other factors (environment) matter too!

Now let’s introduce a new concept which we employ on our operation with regards to CE: percentile rank.

If I’m shopping for a heifer bull, I’m going to establish a CE percentile range I’m comfortable with rather than memorizing one magic EPD number. Why, you ask? Because genetic evaluations change. ASA/IGS recently underwent a CE evaluation update where individual EPD values changed, but most cattle maintained relatively similar % rankings. If I’m not aware of that change and continue selecting bulls based on an old EPD number I’ve always considered “safe,” I could inadvertently be using old criteria on new numbers. That’s why knowing where you’re comfortable at within a population, that sweet spot for % rank can be really helpful.

It’s also important to understand how the breed displays percentile ranks and which direction is considered favorable for each trait. Always check the specific breed Association’s current percentile table and know which direction you’re selecting.

Alright, Seedstock producers it’s your time to shine…this is where our phenotype reporting matters.

This is another reason complete reporting matters. The evaluation becomes more informative when we’re accurately reporting what happened across the entire calf crop, especially first-calf heifers regarding CE. Unassisted vs assisted births. Easy vs hard pulls. Those records help give the evaluation the phenotype information needed to better identify genetic differences in CE.

So…what does this mean to the commercial producer looking for a heifer bull at the sale?

Use CE as a criterion, not your entire breeding objective. If the outcome you’re trying to influence is calving difficulty in heifers, CE is the more direct tool for answering that question. Find the percentile range that fits your comfort level, enough calving ease for your risk tolerance, heifers and management system, then select for the rest of the genetic package you need.

Key Take Aways

BW EPD = expected differences in pounds of birth weight.

CE EPD = expected differences in the probability of unassisted births from first-calf heifers.

*disclaimer, I’m not a geneticist. The information above is compiled from breed association resources and translated into practical terms based on my understanding and application of these tools.