Selection Decisions Committee
Value of DNA Marker Information
for Beef Bull Selection
COLUMBIA, Mo. (June 30, 2010) — When it comes to the use of DNA marker information in bull selection, Alison Van Eenennaam, Extension animal genomics and biotechnology specialist with the University of California, Davis, says producers must decide, "Does it work? Is it useful? Does it pay?"
Van Eenennaam uses a test for marbling as an example. To determine if it works, she first establishes its accuracy.
"Heritability affects how many animals need to be tested. A good rule of thumb is 2,500 animals. We learn that the heritability of marbling is 40%, so even though other genes still contribute and get caught in my expected progeny differences (EPDs), it does work," she says, noting that accuracy here refers to the genetic correlation between the test result and the true breeding value, not the BIF accuracy value. "The more accurate a test is, the more opportunity there is to accelerate genetic improvement."
Whether or not DNA testing is useful depends on the market served. Van Eenennaam says one way to make the decision is to develop a “selection index” that weights all traits on their relative economic importance. Indexes consider the "input," or expense side, of selection decisions and enable cattle producers to make balanced selection decisions. Indexes take into account the economically-relevant growth, carcass and fertility attributes of each animal to identify which animals are the most profitable for a particular commercial enterprise.
To determine if the DNA test pays, Van Eenennaam runs through the economics. In her example, the marbling score was a big driver in the feedlot maternal index, an Australian domestic market. The DNA test improved selection response 90% and added value to the operation amounting to several hundred dollars per bull. When a trait is not a big driver for the market sought, the test may not pay. In addition, even though the test appears to pay on paper, whether or not the producer or processor sees the value depends on the market.
"Seedstock producers need individual estimates of genetic variation explained by a test to determine if it works, its usefulness and whether or not it pays," she says. "DNA tests clearly have the potential to add value for producers, but it is situation dependent.
"Until recently, commercialized DNA tests for beef cattle targeted only a handful of traits. As DNA testing becomes more comprehensive and encompasses more traits, it will become increasingly important to integrate the information into national cattle evaluations," Van Eenennaam concludes. "Making optimal use of the information will likely require concurrent development of multi-trait selection indexes of relevance to U.S. beef production systems."
Van Eenennam spoke during the Selection Decisions Committee break-out session at the 2010 BIF symposium. Themed "Gateway to Profit," the 42nd annual research symposium and annual meeting was hosted by BIF June 28-July 1 in Columbia, Mo.
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