Selecting Superior Sires
“Improvement of next year’s calf crop is dependent upon the breeding decisions producers make,” said Bryan Richard Kutz, instructor and youth specialist in the Department of Animal Science at the University of Arkansas. “Herd sire selection should be a thought provoking and profit driven decision process. Males 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.
An EPD is an Expected Progeny Difference. “It is a prediction of the animal’s genetic value as a parent. In the long run it is wiser to make breeding decisions based on EPDs rather than the bull’s own weaning weight or other measurements,” said Jared Decker, assistant professor of beef genetics extension and computational genomics with the Department of Animal Science at the University of Missouri. “The EPD uses more information to make predictions and accounts for environmental differences between herds and groups of animals. Genomic-enhanced EPDs do a better job of identifying differences between young animals and reduce the amount of risk a bull buyer is taking.”
“This does not predict actual performance of future progeny but rather the difference in average expected performance between potential sires or dams,” Kutz said. “For example, consider two different sires’ weaning weight EPD. Bull A has a WW of 35 and Bull B has a WW of 44. You should expect progeny from sire B to weigh 9 pounds more on average than progeny from sire A.”
• Breed Average EPD: The breed average for a given trait is not necessarily zero. EPDs may increase or decrease over time compared to the base year.
• Accuracy: This is a value that suggests more or less confidence in the EPD. The more information that is collected on that particular animal the more reliable the EPD becomes.
• Hybrid Vigor and Breed Complementarity: Generating hybrid vigor is one of the most important reasons for crossbreeding. Hybrid vigor is the performance a producer will gain by crossing animals of unrelated populations. Breed complementarity refers to the production of a more desirable offspring by crossing breeds that are genetically different from each other but have complimentary attributes.
• Heritability: Reproductive traits typically are very lowly heritable. Most of the variation in reproductive performance is due to the environment and is hard to make changes in one generation. However, carcass traits are very highly inherited and producers can improve product merit very easily.
• Percentile Rank: This is a measure of where that animal ranks in its breed. The 50th percentile is average. Animals in the top 5th 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.
“Economic selection indexes really simplify the decision making process,” Decker said. “Instead of considering dozens of EPD values simultaneously, a producer can focus on one value, the economic index, when ranking animals.”
“An EPD is only one tool a producer can use to make purchasing decisions,” Kutz said. “A producer should also use visual appraisal as a means for sire selection. Structural correctness evaluated as a means of herdsire longevity is extremely important and a trait that is not reported as an EPD.”
Producers should also do everything possible to make sure the bull they are buying is fertile, Decker said. “One way to test the bull’s fertility is through a breeding soundness exam. The veterinarian will also examine the bull for problems with his structure and reproductive organs.
The scrotal circumference (SC) EPD is another way to evaluate fertility. The larger the scrotum, the more high quality sperm the bull will be able to produce.”
For more information, producers should seek their breed association’s sire summaries with EPD definitions, genetic trends and the breeds’ average EPDs.