EPD's help make the best of the herd better

By MONETTE TAYLOR | South Central Texas

Dr. Steve Hammack, left, shares information with Mike McCravey from the Texas Beef Council during the cow-calf clinic in Brenham. -Staff photo by Taylor

November 8, 2001 -- What do we mean by Expected Progeny Difference (EPD) in beef cattle? It is a term that producers are hearing more and more, and a system that has been developed to assist in estimating how the best can be made better.

Dr. Steve Hammack, Extension Beef Cattle Specialist from Stephenville, addressed the group attending the 30th Annual South Central Texas Cow-Calf Clinic held, recently, in Brenham.

"It is a subject that has been around for a number of years. It's not new. It's been fairly slow, especially in the state of Texas, to catch on, compared to some areas of the country," said Hammack.

"Anytime we talk about the whole aspect in the area of genetics, we need to talk about the overall concept of genetics."

Since the early '70s, EPD ... which is based on "within-contemporary-group ratios" was developed to provide such an estimate. According to literature from Hammack, the first practical implementation of EPD was based on the National Sire Evaluation (NSE) that compared sires across an entire breed.

Some assumptions from these tests proved incorrect, and more work was done to attain a better way of predicting genetic outcomes.

Hammack discussed the four, major areas of consideration for producers when considering EPD.

"The first thing that's important is you need to determine what your conditions are ... your production conditions and your market conditions," said Hammack.

Obviously, with different climates, production methods and markets in the area, decisions need to be made by individual producers concerning what will be the most advantageous as well as profitable for their herd.

Next, Hammack said that different types of cattle fit certain conditions better, and different levels of performance concerning growth weights as well as milk production must be considered.

"The third thing is to decide on a breeding system and, basically, what we mean by that is are you saving replacement heifers out of your herd or not. If you are, then there's an additional set of things you've got to be concerned with," said Hammack.

"If you are saving heifers, you have to consider not only how the calves fit the market to go on through to produce beef, but what kind of heifer replacements might be coming out of there."

He said that many producers do not think of these things ahead of time, and make genetic mistakes in programs, depending on which breeding system is used.

"The fourth thing is to choose what I would call breed types. There's about 75 breeds of cattle in the country. It becomes a bit difficult to define. There's only about 12-15 that contribute significant numbers of any sort to the nation's cattle numbers, but you can still get a lot of variation from those 12-15 types," said Hammack.

Once the decision has been made concerning a breed, producers can implement methods of selection of individuals within breeds for certain characteristics, he added.

"All of these things are important in the beef business. Some are more important than others, depending on how many phases of the beef business you might participate in," he said.

"Where you're going to make the most improvement in a beef operation is through sire selection."

Sires have more impact on production than the female because of the number of off-springs that a sire leaves ... usually, a minimum of 20-25 a year. Sire selection is where producers make most of the genetic changes desired for their herd.

Hammack said that 50 years or so ago, comparison was done, largely, by weights, without comparison of age of the calf, mama cow's age, weaning weight, etc. Over the years, progress has been made and the decision was that comparisons must be made by using like ages, times of weight and other like situations.

"EPD is an estimate of the average progenies comparative performance," said Hammack.

He believes that the word, "average," is a more accurate word than "expected," as he feels that "expected" can be misleading, since it implies "a high degree of certainty."

While earlier comparisons used reference sires, most recent programs do not.

"Modern EPD programs no longer have reference sires. They've advanced beyond that, and the mathematics techniques involved ... basically, any animal within a breed that's got a record in more than one group of cattle serves as a reference," said Hammack.

According to Hammack, all breed association programs evaluate the same traits: birth weight, weaning weight, yearling weight and milk, which actually includes any maternal influence. He said that comparisons across-breeds are less accurate than within-breed.

"In summary, EPD is an estimate of true genetic transmitting value in relation to other individuals in a breed," said Hammack.