Economically Relevant Traits
and Selection Indexes
Time has proven expected progeny difference (EPD) values to be effective for selection of genetically superior beef cattle. Based on the assumption that more information about more traits would help to better characterize the genetic merit of potential breeding animals, the number of traits for which EPDs are calculated continued to grow. However, the multitude of EPD values and the volume of performance and pedigree information provided can be confusing to seedstock buyers.
“The challenge for commercial producers is to choose the index that best fits their production and marketing system,” said Mark Enns, Colorado State University geneticist.
“There can be too much information, causing us to throw up our hands,” said Colorado State University geneticist Mark Enns, addressing the Range Beef Cattle Symposium hosted Dec. 3-5, in Rapid City, S.D. Enns said the concept of economically relevant traits (ERTs) and selection indexes can help producers reduce the amount of information needed to make effective selection decisions.
According to Enns, an ERT is a trait directly associated with a production cost or income derived from production. Change for an ERT results in change in either cost or income. On the other hand, change for indicator traits may or may not affect profitability.
Enns used two traits associated with dystocia, or calving difficulty, as examples. Calving ease is an ERT due to its effect on calf survival, dam rebreeding rates, as well as time and expense associated with aiding difficult births. However, birth weight is only an indicator trait of calving ease. Other factors also contribute to whether a heifer or cow experiences a difficult delivery. Therefore, the EPD for calving ease is the better tool when selecting for reduced incidence of dystocia.
“The ERT concept narrows the list of traits to focus selection,” stated Enns, adding that ERTs are not the same for all cattle operations.
Enns described the economic selection index as an extremely attractive option for making genetic selection and purchase decisions. A selection index reflects a combination of ERTs, and the economic value of each, into a single numeric value — often expressed in dollars. An index is used just like an EPD, with the difference between two animals’ respective index values representing the differences expected in the performance of their respective progeny.
“The challenge for commercial producers is to choose the index that best fits their production and marketing system. They have to use it appropriately, realizing that different traits will be emphasized in different indices,” said Enns, “but index selection works.”
If the most appropriate selection index still doesn’t include an ERT on which a producer wishes to focus, the producer will have to consider the EPD for that trait, independently, in addition to the index. By understanding the ERT concept and taking advantage of an appropriate economic selection index, Enns said producers can avoid information overload and make effective selection decisions.
Editor’s Note: Enns spoke Wednesday at RBCS XXIII. Visit the Newsroom at www.rangebeefcow.com/2013 to view his PowerPoint, read his proceedings paper or listen to his presentation.