by Amanda Smith, Associate Editor
Since the Net Merit (NM$) index was developed 20 years ago, it has undergone five revisions as new traits have been added and the relative emphasis on these traits is reevaluated. As an index for commercial dairy producers, the goal of NM$ is to produce cattle that will be profitable under market conditions in three to five years.
At the Joint Annual Meeting in Kansas City, Mo., John Cole, with the Animal Genomics and Improvement Laboratory, highlighted three reasons why the index will be revised for the December proof run. These included new traits that better describe the cow's biology, changing production economics in response to market demands and policy, and changes in evaluation methodology that affect calculations.
"Indices change over time," noted Cole. "Higher milk prices, driven by exports, warrant placing more emphasis on production," he added.
Compared to the 2010 revision, more emphasis will be placed on production (from 35 to 44 percent). Meanwhile, the productive life (PL) value was reduced, by 3 percent, as was the emphasis on fertility (from 11 percent to 9 percent). "Fertility traits, too, benefit from a multi-trait analysis," said Cole. Within the fertility grouping, two traits, heifer conception rate (HCR) and cow conception rate (CCR), have been added.
While the updated formula will not be incorporated until the December proof run, next week's Hoard's Dairyman Intel (August 18) will contain a link to the August Hoard's Dairyman Bull List.