Although snow is still on the ground, in many places so are new born calves. In a few months the winter snow will be a past memory and we will be relishing the green grass and the start of the breeding season.
Before the breeding season gets here however, we have to be prepared. Involved in the preparedness is selecting the appropriate sire, either AI or natural service bull, that will best fit the needs of your herd and produce the type of calves you and the market desires.
Producing quality beef does not occur by happenstance, but rather is the product of a comprehensive, whole system approach, to cattle production and management. Involved with whole system approach is sire selection. Within most herds, most of the genetic progress is due to sire selection. Selecting a sire that does not have the genetic composition to improve or maintain your herd has dire long-term consequences.
Within each breed great variation of productivity exists between animals, hence knowing how to properly select an animal using genetic tools is critical. To assist with selecting breeding stock that have the phenotypic traits of economic performance, producers should use Expected Progeny Differences (EPDs). EPDs are a measure of genetic value that can be used to compare traits of economic importance between animals within a breed. EPDs are designed to compare animals within a breed for their genetic merit.
Recently, across-breed EPD adjustments are available, thus allowing animals across breeds to be compared. To find out more about across-breed EPDs and how to use this genetic tool visit: http://www.angus.org/Nce/AcrossBreedEpdAdjFactors.aspx.
At their core, EPDs provide two key pieces of information: the actual EPD and the accuracy of that prediction. Depending upon the trait, EPDs can be positive (+) or negative (-) and represent various units such as pounds (birth weight [BW], weaning weight [WW]), centimeters (scrotal circumference), inches (hip height), degrees (marbling), or an index of multiple traits combined and estimated economic value (Angus Beef Value; $B).
These values are meant to compare animals of the same breed and provide an estimation of the difference expected to see between progeny due to genetics. Remember, EPDs do not account for environmental or managerial differences animals may receive, only genetic potential. For example, Bull A with a weaning weight EPD of +30 would be expected to deliver 20 additional pounds of weaning weight compared to a Bull B with a weaning weight EPD of + 10.
EPDs are not a stagnant value; they change as more data are collected on that animal and its offspring. Therefore, the second number provided, below the actual EPD, is the accuracy value (ACC), or the estimate on how accurate that prediction will be. The higher the ACC, the more reliable the EPD value.
Accuracy values less than 0.45 are considered to be lowly reliable, between 0.65 and 0.75 moderately accurate, and greater than 0.75 highly accurate. As more progeny are evaluated for a bull, the accuracy will increase.
When using EPDs for animal selection there are key things to remember.
Compare animals of the same breed for genetic merit of a selected trait. Remember, however, an animal’s performance is controlled by both genetics and environment. Hence, in addition to genetics, environmental factors impact actual animal performance.
When comparing two animals, the EPD difference indicates the differences expected to be seen in progeny due to genetics.
EPDs are a tool to increase, decrease, or maintain any trait of interest.
EPDs are not designed to compare between breeds. With that said, mechanisms exist to compare EPDs across breeds (as detailed in link provided above), but additional calculations are required.
EPDs don’t predict outcomes but allow you to compare the potential genetic contributions between animals.
An EPD of zero is not average; breed associations update averages yearly.
EPDs change, as do the averages for EPDs.
Most importantly, EPDs do not make up for poor management.
When using EPDs to select animals consider the following tips:
– Prioritize the traits of economic importance and those that significantly contribute to profitability in your marketing plan. There are numerous EPDs, select those that are most impactful to profits. A great sire for your ranch doesn’t necessarily have to have excellent numbers in each category, just those important to your end goals.
– Match traits selected to the environment. Genetic potential is useless if environmental constraints prevent animals from reaching their genetic potential. For example, although an extremely high EPD for milk production may look impressive, consider the feed resources required to support such production. If your operation can’t offer that, a more moderate number for milk would be desirable.
– “Optimize” rather than “Maximize.” Avoid selecting animals based on a single trait. Use a well-rounded approach and select animals with multiple traits that are above average for that breed. If calving ease is important, don’t simply search a bull catalogue for the sire with the best calving ease, but rather establish a minimum you are willing to accept and then select a bull that best fits your operation that falls within the limits you have established.
– Especially when purchasing bulls, make sure his physical attributes match up with what you see on paper. Bulls should always be evaluated for both breeding soundness as well as structural soundness before being purchased. EPDs are irrelevant if a bull cannot cover cows.
If you have any further questions, please contact Dr. Allen Bridges firstname.lastname@example.org; 218-327-4615) or check out the University of Minnesota Beef Team website at www.extension.umn.edu/beef.
(Allen Bridges, Ph.D., is a reproductive physiologist at the North Central Research and Outreach Center in Grand Rapids, Minn., and Shantille Kruse is a Ph.D. graduate student there.)