Genetic decisions made by both seedstock and commercial producers can be extremely complex. In fact, by some estimates there are up to 72 genetic traits that can be measured and ranked for expected progeny differences (EPDs). But according to Bruce Golden, animal breeding specialist at Colorado State University, there are only between 10 and 12 traits in cattle that influence profitability. Many, if not most, traits that are measured do not directly affect profit.

Economically relevant traits

"Birth weight, for example, is measured not because a producer gets more or less money due to the weight of a calf at birth. Rather, birth weight is used to help predict the probability of a difficult birth for the progeny or grand progeny of a sire," explains Dr. Golden.

To better understand the concept of economically relevant traits, Dr. Golden offers an example. Ask yourself, "Which would have a greater impact on profit margin-heifer pregnancy or scrotal circumference?" Testicular size by itself does not hold any direct economic value to the commercial producer. But, scrotal circumference in a sire is favorably correlated to the age at which the sire’s daughters will reach puberty. Age at puberty is still not a trait for which the commercial producer receives any direct income. Rather, age at puberty indicates the ability of daughters to conceive and have a calf as two-year-old heifers. And since there are additional genetic factors influencing a heifer’s ability to sustain pregnancy, they will not all be accounted for by scrotal circumference.

"What we really want to improve is not scrotal circumference. We want to improve heifer pregnancy," says Dr. Golden. "Scrotal circumference explains part of that, but the best indicator of heifer pregnancy is pregnancy observations."

Economically relevant traits are the traits that directly affect profitability by being associated with a specific cost of production or an income stream from the sale of a product. Traits such as birth weight or scrotal circumference, which are used to indicate the merit an animal has for another trait, are called indicator traits. Virtually every economically relevant trait in beef cattle production has multiple indicator traits available.

"Evaluating the economically important traits reduces the amount of information that you have to assimilate and directly focus on the things that control profit," says Dr. Golden.
Sire summery of the future

Dr. Golden’s vision for the sire summary of the future identifies 12 economically important trait EPDs that have been or could be developed (see sidebar). His list contains just the most obvious indicators, as it is likely that different situations will be able to use other indicators.

"It allows us to have fewer EPDs that more directly cover traits of interest. You can have any number of indicator traits but if you just go to the trait of interest you don’t have to have all of those indicator EPDs."

Dr. Golden says that although his list has 12 economically important traits identified, any one producer would probably only use nine of these at one time.

"We need weaning weight because most producers sell calves at weaning. Weaning weight is their economically important trait so they should ignore the yearling weight EPD," says Dr. Golden. "Conversely if you sell calves as yearlings you should ignore the weaning weight EPD. But we have to have both EPDs in a sire summery because different producers use them differently."

Developing reproductive EPDs

Despite the economic relevance of improved reproductive efficiency, little emphasis has been placed on reproductive trait EPDs. One reason is the perception that female fertility measures are lowly heritable and therefore difficult to change. In fact, low heritability is why researchers sought out indicator traits to better identify the animals with the most desirable reproduction traits. But recent studies at Colorado State University indicate that heritability estimates for heifer pregnancy are higher than previously believed. In fact they are moderately heritable for some cattle populations.

In a cooperative effort between the Colorado State University’s Center for Genetic Evaluation of Livestock and the Red Angus of America Association, geneticists focusing on economically important traits have developed new predicators for fertility.

"The goal of the Red Angus Association is to characterize three areas of profitability which include reproduction, growth and carcass traits by utilizing the fewest EPDs to achieve that purpose," says R.L. Hough, Executive Secretary of the Red Angus Association of America. "Reproduction is by far the most economically important trait so that has been our recent focus."

Probably the most expensive function in a cow-calf operation is developing replacement heifers. For example, if a 500-head cowherd has a 20 percent replacement rate, a 90 percent pregnancy rate and weans a 90 percent calf crop, then it needs to retain 49 percent of its heifers each year. And the expense of developing 100 replacement heifers can easily reach $95,000 per year.

The Red Angus Association has developed a prototype heifer pregnancy EPD from herds with heifer pregnancy databases.

"We look at two areas for fertility. Do they successfully enter the herd and do they stay in the herd producing past six years of age? These EPDs are expressed as percent probability," says Dr. Hough. "The stayability EPD has been fully developed and implemented, and we are well on the road to developing and implementing the heifer pregnancy EPD. We have collected all of the historic data for our prototype run and we are now in the process of collecting one year’s worth of field data."

There are several reasons heifer pregnancy is an ideal EPD to develop. It is economically relevant, data are easy to record, pregnancy detection methods are established, analytical procedures are available, and the heifer pregnancy EPD is expressed on the same scale as stayability. Heifer pregnancy EPDs are reported as the percent probability that heifer progeny exposed to a bull will conceive and calve as a two-year-old.

The benefits

Economically relevant traits can assist producers in maximizing profit and reducing the risk of their genetic selection decisions. Another benefit is that by having the economically relevant trait EPD available, producers and breed associations can assign a dollar value to each economically-relevant trait and sum the results to produce an EPD for profit.

Perhaps the greatest benefit to including all economically relevant traits in future national cattle evaluations, according to Dr. Golden, is that producers will have a clearer understanding of the relationship between their selection decision and profit.