“Understanding the reproductive performance of sires being selected for breeding is vital to the success of a cow-calf operation,” said Bryan Richard Kutz, instructor and youth specialist for the Department of Animal Science at the University of Arkansas. “Because a bull is expected to service various numbers of cows, the potential fertility of the bull is much more important than determining the fertility of any individual cow.”
According to Jared Decker, assistant professor, beef genetics extension and computational genomics at the University of Missouri, prioritizing traits should include identifying your market endpoint and economically relevant traits for your operation.
“Producers need to take an inventory of their cattle and identify which traits need more emphasis in their herds,” Decker said.
These traits could include addressing items such as calving ease issues or weaning weights.
“Some breeds may have up to 20 EPDs or other terms to consider,” said Eldon Cole, livestock specialist for Extension at the University of Missouri. “I recommend when selecting sires either for natural or artificial insemination, a person go online to the website for the breed of interest and study their sire summary. These summaries carry a glossary of the various terms and how to interpret the numbers.”
The summaries also have percentile rank table for bulls, cows and young animals. “This is an easy table to use and determine if an animal in the top (1 percent) or bottom (99 percent) for a particular trait in the breed,” Cole said. “An animal with a 50 percent rank is considered average for that trait in that breed. Each breed has its own unique EPD system so make comparisons within a breed.”
Regarding items not represented in an EPD, Kutz suggested that potential bull buyers question information about Pedigree, temperament, visual and physical attributes and prior feeding regimen.
Other considerations should include making sure the bull has passed a breeding soundness exam, has been tested for diseases such as Brucellosis and Trichonomiasis, and is able to easily maneuver about the pasture.
“A producer today has a wealth of data they can and should use to select sires,” Cole said. “The more you know about your cow herd’s strengths and weaknesses, the easier it is to search for the genes to make the appropriate adjustment.”
The new table of adjustment factors to be used to estimate across-breed EPDs for 18 breeds has been released for 2013 by the U.S. Meat Animal Research Center. Bulls of different breeds can be compared on the same EPD scale by adding the appropriate adjustment factor to the EPDs produced in the most recent genetic evaluations for each of the 18 breeds.
Producers can learn more about EPDs and other selection terms by contacting extension specialists, the field staff of the breed association from which they are purchasing bulls or semen, their regional livestock specialists or their state beef genetics specialist.
“Improvement of next year’s calf crop is dependent upon the breeding decisions producers make,” Kutz said. “Herd sire selection should be a thought provoking and profit driven decision process. Male’s account for approximately 90 percent of the gene pool, contributing more to the genetic makeup of a herd in one breeding season than a cow contributes in her lifetime. Selecting genetically superior sires is the fastest approach to herd improvement and ultimately bottom line profitability.”
A Few Basic Terms
• Expected Progeny Difference (EPD): The variation in expected performance of the calves sired by a bull compared to expected performance of calves sired by another bull.
• Breed Average EPD: The breed average for a given trait is not necessarily zero. Zero represents the average genetic merit of animals in the database at the time when there was sufficient information to calculate EPDs which is termed the Base Year. If the breed has made any genetic change over time then the average EPD is likely to change. EPDs may increase or decrease over time compared to the base year.
• Accuracy: A measure of confidence in an EPD. Accuracy is influenced by the amount of progeny data and the distribution of those progeny across herds.
• Hybrid Vigor and Breed Complementarity: One of the most important reasons for crossbreeding and essentially the additional performance a producer will see by crossing animals of unrelated populations. Breed complementarily refers to the production of a more desirable offspring by crossing breeds that are genetically different from each other but have complementary attributes.
• Heritability: The amount of variation in a trait due to genetics, rather than other factors.
• Breeding Soundness Exam: an examination by a veterinarian of the appearance, the reproductive organs, and the semen quality of a bull.
• Percentile Rank: This is a measure of where that animal ranks in its breed. The 50th percentile is average. Animals in the top 5 percentile are superior to 95 percent of the animals in the breed.
• Economic Index: An economic index combines estimates from multiple EPDs with the trait’s economic importance to report a single index to use in selection decisions.
• Calving Ease Direct (CED): An EPD expressed as the difference in the percentage of unassisted births. If Bull A has a CED of 8 and Bull B has a CED of 3, we would expect to see 5 percent fewer calving problems with Bull A’s progeny. This EPD is favored over a birth weight EPD because it takes more information into account.
• Birth Weight (BW): Pounds of expected birth weight difference between two or more bull’s or females.
• Weaning Weight (WW): Expressed in pounds of weaning weight difference between two or more bulls or cows.
• Yearling Weight (YW): Pounds of difference in 365-day weight between two or more bulls or cows.
