Much of that improvement is due to the implementation and use of expected progeny differences (EPDs). Since beef cattle are marketed on the basis of weight, and in some cases by carcass merit, most EPDs reported in breed association sire summaries involve growth traits and carcass traits.
Often, selection for reproductive traits has been overlooked even though reproduction (fertility) is key to a beef operation’s bottom line.
Reproductive efficiency (fertility) determines to a great extent the profitability of the beef cattle enterprise.
Income from a beef cattle herd comes from the sale of progeny or the sale of salvageable animals in the breeding herd itself.
There is no question the level of importance reproduction has when compared to other traits. In a commercial beef cow herd, improvements in reproductive traits can be four times more important than improvements in carcass traits.
More recently, an evaluation of the relative economic weights of various trait categories was conducted on approximately 110,000 records from the American Gelbvieh Association’s Gelbvieh Alliance marketing program.
The estimated relative importance of reproductive traits, growth traits and product traits was approximately four to two to one, respectively.
Reproductive efficiency also has an indirect role in determining profit since it is largely responsible for the amount of selection pressure breeders might exert in their efforts to increase production levels through genetic improvement of their herds.
These studies, as well as others, suggest that selection for reproduction is required to maximize profitability in the beef cattle enterprise.
While it is evident reproductive traits should receive the greatest emphasis in selection programs, producers should be diligent not to overlook reproduction and at least place it on an equal level with production and product traits in selection protocols.
However, results from a recent survey suggest that reproductive traits may not be receiving the attention they deserve in selection programs.
Historically, beef producers have found it difficult to select for, and improve, reproduction or fertility.
This is due, in part, to reproduction being comprised of a variety of traits and little agreement on how reproduction should be described or defined.
In a review of reproductive traits and their heritabilities, definitions of reproductive traits are stated to vary across cattle species, breeds, locations, sexes and animal classes.
The complexity of reproduction and the lack of agreement on how reproduction should be defined and evaluated has resulted in a longer development and slower adoption of genetic improvement programs.
In addition, the review reported heritabilities for reproductive traits to be moderate to low. (Heritability indicates the amount of variation in a trait that is due to genetics and indicates how a trait will respond to selection.)
Despite facing some hurdles, beef producers do have tools at their disposal to assist them in improving reproductive traits.
Expected progeny differences (EPDs) represent the beef industry’s most powerful source of information for selection and genetic improvement. EPDs are the best estimate of an animal’s genetic worth.
EPDs are calculated by breed associations and presented in the breed associations’ sire summaries.
Before implementing a selection protocol, producers should define their production goals, set minimum performance standards for each trait of interest and evaluate their herd.
After the directions are set, producers should select breeding animals that are superior for the traits of interest and animals that will allow productions goals to be met.
Listed below are EPDs producers can use to affect the reproductive performance in their breeding herd.
• Birthweight – Birthweight EPDs are expressed in pounds and represent the sire’s ability to transmit birthweight to his offspring compared to other sires.
Larger values indicate greater birthweights. Birthweight EPDs may be used to keep birthweights in check in a breeding herd and alleviate calving difficulties.
• Calving ease (direct) – Calving ease (direct) EPDs are expressed as a difference in percentage of unassisted births and predict the difference in ease with which a sire’s calves will be born when he is mated to first-calf heifers.
Larger values indicate greater calving ease (larger percentage of unassisted births) in first-calf heifers. Calving ease (direct) EPDs may be used to assist in preventing and diminishing calving difficulties in a breeding herd.
• Calving ease (maternal) – Calving ease (maternal) EPDs are expressed as a difference in percentage of unassisted births and predict the difference in ease with which a sire’s daughters will calve as first-calf heifers.
Larger values indicate greater caving ease (larger percentage of unassisted births) in a sire’s daughters. Calving ease (maternal) EPDs may be used to assist in preventing and diminishing calving difficulties in a breeding herd.
• Heifer pregnancy – Heifer pregnancy EPDs are expressed as a difference in percentage of a sire’s daughters conceiving to calve at 2 years old.
Larger values indicate larger numbers of pregnant heifers. Heifer pregnancy EPDs may be used to improve reproductive efficiency in a breeding herd.
• Scrotal circumference – Scrotal circumference EPDs are expressed in centimeters and represent the sire’s ability to transmit scrotal growth to his offspring compared to other sires.
Larger values indicate greater scrotal circumferences. Scrotal circumference EPDs may be used to improve reproduction in breeding herds through improved semen traits (males) and decreased age of puberty (males and females).
• Stayability – Stayability EPDs are expressed as a difference in percentage of a sire’s daughters remaining in the breeding herd until at least 6 years old.
Larger values indicate larger numbers of cows remaining in the breeding herd for longer periods. Stayability EPDs may be used to improve reproductive efficiency in a breeding herd.
Due to the impact reproductive efficiency (fertility) has on a beef cattle enterprise’s profitability, it warrants accurate evaluation and careful consideration in beef cattle selection.
Even though producers face challenges in selecting for improved reproduction, tools (EPD, etc.) are available to assist them along the way. 
References omitted due to space but are available upon request. Click here to email an editor.
PHOTO
Reproductive efficiency (fertility) determines to a great extent the profitability of the beef cattle enterprise. Photo by David Cooper.
J. Benton Glaze, Jr.
Extension Beef Cattle Specialist
University of Idaho
