BEEF Editors' Blog

Despite All The New Selection Tools, Calf Birthweight Still Rules?

A recent survey by BEEF shows a bull’s actual birth weight is the most important trait for bull buyers.

Many years ago, when I was what Earl Butz once described as a lump of clay, ready to be molded, I was a student worker with the cow herd at the institution of higher learning I was attending. Back then, the folks who were trying to mold all us lumps into something they thought would be useful to the beef industry were chasing all the growth genetics they could find. Bigger is better seemed to be the mantra.

And, within reason, it is. However, back in those dark ages, all we had to work with was actual performance data—EPDs were just coming on the scene and a bull’s actual birthweight, 205-day adjusted weight, and yearling weight were the performance data that ruled.

As a result, calving season became a “teachable moment” for both the molders and the moldees. I can’t recall the numbers, but I can vividly recall pulling a lot of calves that year. And not just in the heifers, although they were the epicenter of the wreck—we pulled plenty of calves from the mature cows as well.

Among the many lessons we all learned was that just because a bull had a light birthweight didn’t necessarily mean he was an easy-calving bull.

Fast forward more years than I’m going to admit to. We’ve come a long way in our understanding of genetics and genetic interactions in those years, and not only do we have very solid EPDs to guide our decisions, but a growing understanding of genomics.

It was thus with eyebrows raised high that I looked at the results of a recent survey that BEEF magazine did of its readers. You’ll read a more complete rundown of the survey results in the February magazine, but the answers to one question caught my attention as they sent me on a not-so-memorable trip down memory lane.

Here are the top five responses when we asked “Which of the following information do you require to purchase a bull?”:

  • Actual birthweight—72.9%
  • Birthweight EPD—68.6%
  • Calving Ease-Direct EPD—58.5%
  • Actual weaning weight—55.3%
  • Weaning weight EPD—52.9%

What raised my eyebrows in this data was the reliance on a bull’s actual birthweight and weaning weight in the decision-making process of whether or not a buyer raises a hand to bid on a bull. Here’s why.

“Of the genetic variation in calving ease, birthweight only describes 47%,” says Bob Weaber, Kansas State University Extension cow-calf specialist and one of a handful of my go-to guys when I have a question on genetics, which is often. “So you leave the other half on the table when you just focus on birthweight. We know birthweight genetics play a role in calving ease, but birthweight alone doesn’t describe all the genetic variation in calving ease. Other factors like calf shape and muscularity play a role too.”

Weaber says it’s important to also recognize that genetics don’t control all the variation in calving ease or dystocia. Environmental factors such as cow nutrition during gestation, among many others, play a big role in a calf’s ability to express its genetic potential. “The heritability for calving ease in Angus is 0.2, which means 20% of the variation in phenotype (or a calf’s actual performance) is under additive control; 80% is environmental,” Weaber says. “Birthweight has a heritability of 0.42 in Angus. So about 42% is genetic control, 58% is environmental.”

In spite of the fact that birthweight is more heritable than calving ease, Weaber recommends that if you’re looking for an easy-calving bull, focus on the calving ease EPD. That’s because it combines multiple traits, including the bull’s (or its sire’s) calving ease score, among other things, as well as its actual birthweight.

For cow-calf producers, calving ease is the economically relevant trait. Birthweight is an indicator trait. Birthweight provides some information on calving ease, but birthweight alone doesn’t directly generate revenue or incur costs. “Calving difficulty or dystocia is what gets you in your hip pocket,” Weaber says.

The other consideration with selecting for birthweight only is that it has a fairly strong correlation with other growth traits, Weaber says. Reducing the birthweight may lead to decreased performance at weaning and yearling.


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Thus, he recommends that if you’re selecting bulls to use on first-calf heifers, look for bulls with a calving ease EPD in the top 20% of the breed. In most breeds, it is relatively easy to find calving ease bulls with desirable levels of growth; bulls that beat the genetic antagonism between calving ease and growth, he adds.

I understand why actual birthweight and weaning weight are attractive indicators. Those are numbers you can wrap your brain around. They mean something because they’re real-world. EPDs and genomics, on the other hand, are not numbers that intuitively make sense without a deeper understanding of what they mean. But in the highly complicated world of genetics, focusing on a bull’s actual performance data alone can lead you into a wreck if you’re not careful, as we learned those many years ago.

“Some people fall into the trap that birthweight has a higher heritability than calving ease, so if you select on birthweight, you make more progress,” Weaber says. “Well, you’ll make more progress on birthweight; you won’t make more progress on calving ease. So put the selection pressure on calving ease. You’ll sleep better during calving season and your heifers will appreciate your astute use of genetic prediction tools.”

What are your thoughts on this discussion? Which selection traits are most important in your program and why? Leave your thoughts in the comments section below.


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Discuss this Blog Entry 6

John R. Dykers, Jr (not verified)
on Jan 8, 2014

All the useful data depend first on accuracy/honesty!
EPD's are derived from measured data. Calving ease is certainly what is most desired, and Mamma Cow has some say in that.
What we are really missing is measuring calf length/height! Mamma can birth a 300 lb snake and get killed by birthing a 10 pound bowling ball! Birth weight is simply relatively easy to measure, yet it is amazing how much of that is done inaccurately.
Build a scale/cage to mount on the front of your calving truck and you can easily get accurate wt and height/length measures on newborn calves while having and easy stage for putting in ear tags, etc.

Anonymous (not verified)
on Jan 8, 2014

"All the useful data depend first on accuracy/honesty!"
I couldn't agree more! While BW EPD depends solely on ratios, comparing each individual to their contemporary group within herd, CE Direct depends on honest reporting of calving problems. For one, purebred herds usually calve bigger heifers than commercial herds thus incurring less dystocia. Bigger heifers can have bigger calves. Also, many purebred breeders do not like to report pulling calves, especially if it is on there hot new AI sire because it wrecks their EDP's.
So while CED is a tool in selecting for calving ease, using it without any consideration for BW EPD can definitely get a commercial cowman in quite a wreck when it comes time to calve heifers.

South Wind (not verified)
on Jan 8, 2014

The number one issue here is the heifer. "Can she calve a breed average wt calf?". So if you have the right kind of heifers and they are bred to a moderate to low birth wt/calving ease bull most will do fine if managed correctly. Remember the cow has to breed on time, carry the calf 283 days under range conditions, go into labor, deliver the calf, get up right away and get the membrane off his face, chase the coyotes off, and get the calf up and feed it. No EPD's for any of those things, but that's where the money is.

on Jan 8, 2014

It's a given that the EPD must be accurate and honestly obtained and must be based on "whole herd reporting". Data obtained otherwise, in my opinion, is worthless.

I never look at birthweight when selecting a bull. I look at CED, Weaning Weight EPD, Maternal, Milk Maintenance Energy (I use Red Angus bulls) Longevity. I heavily weight the CED and look for moderate improvements in the others. A live calf with an unassisted birth is better than a big dead one!

I place a lot of emphasis on both CED and ME for replacements .

My experience is that cows that a fed properly throughout their pregnancy (I don't mean over feeding but meeting the cows nutritional requirements especially during the last trimester) have energetic calves that get right up and nurse and the cows milk well and breed back. I believe these are mainly management issues not EPD determined traits

Anonymous (not verified)
on Jan 10, 2014

We need to also remember that the shape of the calf is primary to CE. A heifer can calve a 3# + BW calf if the shoulders are properly set. An upright (posty-type) set in shoulders is going to get you in trouble with heifers. Besides, if a bull has a long reach and drive, he is going to cover more cows with more ease thus less weight loss and more calves. I don't see how shoulder set can be rated for an EPD except by proper pictures sent in to a central place to "read" them which is unlikely to happen. Therefore, selection pressure is on the herd manager. Look for better structure in your bulls which means more reach in the front and more drive in the rear. You might get a little more hocky-ness, but you will add two positives to your herd--CE and better gains. And a little more hock isn't going to hurt your bottom line (though an excess might).

on May 7, 2015

"Figures don't lie but liars figure"-an old polled Hereford breeder. After 35 years of weighing and tagging calves I believe the most accurate selection tool is the birth wt epd. There is far more data in breed association databases pertinent to it than CED. I agree that a lot of assisted births go unreported. Even if a breeder lies about birth weights it is a lot harder for him or her to rig the ratios than it is to simply not report pulling a calf. The actual birth wt is the poorest selection tool of all-sometimes I would about as soon not even have it-just go by the parents birth epds-provided a visual appraisal and trust in the breeder leads me to believe the pedigree is correct.

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Everyday musings from BEEF Editors on the latest beef industry news and events.


Burt Rutherford

Burt has more than 35 years of experience communicating about beef industry issues. A Colorado native and graduate of Colorado State University with a degree in agricultural journalism, he now works...

Wes Ishmael

Among the industry’s most insightful thinkers, Wes Ishmael concentrates on industry price and market perspectives for BEEF magazine. Along with his monthly “Cattle Economics” column...

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