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Use Net or Fluid Merit to guide service sire selection
Dairy Pipeline: March 2001
Bennet Cassell
Extension Dairy Scientist,
Genetics and Management
540/231-4762
Email: bcassell@vt.edu
The Merit indexes published by USDA were changed back in August to more fully reflect the influence of health and fitness traits on lifetime economic merit and to express genetic superiority for production on a lifetime basis. The numbers associated with the new indexes are different from the previous version or from the MFP$ index that was used throughout the industry for many years. Holstein bulls need Net or Fluid Merit values of about $400 or higher to be in the top 20% of the active list. For Jerseys and Brown Swiss, Net or Fluid Merit values of about $370 put them in the top 20%. For Ayrshires and Guernseys, Net Merit would need to exceed $350 for the bull to make the top 20%, but Fluid Merit values of $400 or higher would be needed to achieve the same rank. The average Net Merit rating for 600 active AI Holsteins (February 2001 proofs) is $317 and ranges from a low of -$335 to a high of $675. The average for 100 active AI Jerseys is $277 and ranges from a low of -$41 to $471. If you look at individual cow evaluations, you will see Merit ratings that are outside of this range. Cows are always more extreme than bulls because there are so many more of them with evaluations. The units for Net or Fluid Merit are dollars of net lifetime genetic value. Traits used in both Merit indexes (with different weights to reflect value of milk in different markets) are PTA's for milk, fat, protein, productive life, somatic cell score and type composites for udders, feet and legs, and size. Production traits receive about two thirds of the total emphasis in Net Merit while productive life receives about 14%, somatic cell score about 9%, and the three type composites about 15% emphasis in total. The combination of traits and weights used make the Merit indexes the most comprehensive ever published by USDA, and the most useful for commercial producers.