The lifetime merit indices promote a balance of traits to maximize dairy cow profitability. These CDCB indices estimate the difference in lifetime profit that each animal is expected to transmit to its progeny, expressed in U.S. dollars.
Indices are valuable tools in cattle breeding because they combine many traits into a single value that drives genetic progress, ranks animals, and streamlines management decisions. Net Merit accounts for nearly 40 traits, including yield, conformation, health and fitness, fertility, and feed intake. Some traits are represented through composites, such as calving ability, health dollars, udder, feet and legs, and body weight.
When a trait has both economic value and genetic variation, including it in the lifetime merit indices increases profitability for dairy herds using the index.
Traits are weighted based on their genetic impact on farm profitability.
The lifetime merit indices are updated periodically to reflect new traits, new research, and current dairy market data. The April 2025 update corresponded to price changes in the dairy market by placing more emphasis on butterfat, cow livability, and heifer livability compared to less emphasis on protein and productive life. Additionally, Body Weight Composite received more negative emphasis, and Residual Feed Intake gained emphasis.
Net Merit (NM$) was introduced in 1994 by renowned USDA geneticists who continue to conduct research that modernizes the U.S. genetic evaluations.
CDCB publishes four lifetime merit indices that are expressed similarly but differ in the emphases assigned to various traits. Net Merit fits the milk market and management system for many U.S. dairy herds. Cheese Merit, Fluid Merit, and Grazing Merit estimate profit potential in specific milk markets and grazing herds.
Lifetime Cheese Merit $ (CM$) is designed for herds that sell milk for cheese, using cheese yield pricing. Cheese Merit factors in the same traits as Net Merit, but it assigns a negative economic weight on PTA Milk and places more emphasis on Protein Pounds because protein has more value in the cheese market. Low somatic cell score (SCS) is prized in this index as high SCS in milk reduces cheese yield.
Lifetime Fluid Merit $ (FM$) fits farms that sell into the fluid milk market. While Fluid Merit combines the same traits as Net Merit, there is considerably more weight on PTA Milk. Protein has no influence in Fluid Merit, as there is little (if any) payment for protein in fluid markets.
Lifetime Grazing Merit $ (GM$) was created for pasture-based herds using intensive grazing. Relevant economic values and trait weightings reflect this herd management. As grazing herds often calve seasonally, fertility receives more emphasis (2.5 times more) than in the other three indices. Production yield, longevity, livability and udder health also differ. Read more in this published paper.
By breed, the formulas for lifetime merit indices differs slightly, because some U.S. traits are not available for all breeds. For Holsteins, evaluations are published for all major U.S. traits. The traits for feed intake, health, heifer livability, stillbirth, and calving ease are not evaluated in all breeds. Breed differences are described in this 2021 USDA paper.
Most U.S. breed associations have developed customized indices that align with goals set by the breeders, such as Total Performance Index (TPI™) in Holsteins and Jersey Performance Index (JPI).
Genetic indexes are updated periodically to add traits, incorporate new research and reflect current economics.
First national composite genetic index published by USDA
Composite indices that combined milk traits and type available
Lifetime merit indices introduced by USDA, accounting for income and cost in production, fitness, and conformation traits. This blend was unique from indices in most countries.
Udder Composite, Feet and Legs Composite, and Body Weight Composite added
Daughter Pregnancy Rate added
Calving traits considered through sub-index
Heifer Conception Rate and Cow Conception Rate added
Cow Livability added
Disease resistance through health trait sub-index
Residual Feed Intake, Heifer Livability, and Early First Calving added
Component, livability, and feed efficiency trait emphases updated to reflect industry price trends
