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Use "Merit" Indexes to Evaluate Service Sires

Dairy Pipeline: May 1999

Bennet Cassell
Extension Dairy Scientist, Genetics and Management
Virginia Tech
(540) 231-4762

One of the useful pieces of information in DHI herd summary sheets is the genetic profile of current service sires. Choice of service sires is where the rubber meets the road in terms of genetic improvement, as the best opportunity dairy producers have to improve genetics is through use of high ranking AI bulls. For several years, DRMS Raleigh has given herds the choice of MFP$, MF$, or CY$ as the measure of service sire merit used on their herd summary sheets. This past February, USDA combined these three indexes with two other genetic evaluations, productive life and somatic cell score into one of three "Merit" indexes. DRMS Raleigh changed their system to use the Merit indexes in place of the three previous options. Almost all Virginia herds have used MFP$ in the past. Service sire merit in those herds is now based on Net Merit, the merit function that includes MFP$. Alternatively, herds could choose MF$ (Fluid Merit) or CY$ (Cheese Merit) to evaluate service sires. Fluid Merit is the index that matches Virginia milk marketing conditions the best, as no protein premiums are paid within the state and Fluid Merit does not give value to pounds of protein in a bull's proof. Leaving your herd on the MFP$ option won't affect your impression of the merit of bulls much as Fluid and Net Merit are closely related. I would caution against using Cheese Merit because it places a high value on protein and a negative weight on milk volume. Virginia milk simply isn't valued that way in the marketplace. The choice of which merit index to use on DHI records isn't nearly as important as deciding to use high ranking proven bulls as service sires. A good goal is to keep average rank of proven AI sires at the 80th percentile or higher.

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